Journal of the Meteorological Society of Japan. Ser. II
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Volume 85A
Special Issue: Coordinated Enhanced Observing Period(CEOP)
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Special Issue on Coordinated Enhanced Observing Period(CEOP)
Article
  • Masayuki HIRAI, Takuya SAKASHITA, Hiroto KITAGAWA, Tadashi TSUYUKI, Ma ...
    Volume 85A (2007) Pages 1-24
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    The operational global numerical weather prediction model at the Japan Meteorological Agency (JMA) currently adopts a Simple Biosphere (SiB) model. JMA has been developing a new SiB model (New-SiB) as an upgrade to the current SiB model (Op-SiB). New-SiB has improved treatment of soil and snow processes compared with Op-SiB. The results of integration experiments performed over a period of 3 years indicate that New-SiB predicts snow-covered areas more accurately than Op-SiB. Moreover, the monthly mean surface air temperature during the polar night is better simulated using New-SiB. To validate the diurnal cycle of near-surface meteorological elements in New-SiB, short-range forecasts obtained using the two SiB models are verified using CEOP (Coordinated Enhanced Observing Period) in situ observation datasets for the Enhanced Observing Period 3 (EOP-3). New-SiB generally simulates diurnal variations in near-surface temperature more accurately than Op-SiB, especially over snow-covered areas; however, the short-range forecast experiments also reveal a number of shortcomings in both models. The CEOP datasets are highly valuable in evaluating numerical weather-prediction models.
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  • Sin Chan CHOU, José A. MARENGO, Claudine P. DERECZYNSKI, Patric ...
    Volume 85A (2007) Pages 25-42
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    We compared forecasts of the Center for Weather Prediction and Climate Studies (Centro de Previsão de Tempo e Estudos Clim´ticos—CPTEC) General Circulation Model (GCM) and the mesoscale Eta Model with observations undertaken at the Rondonia Coordinated Enhanced Observing Period (CEOP) reference site, Brazil, for the dry period between 1 July and 1 September 2001. The Rondonia site is located in the Jaru Biological Reserve Area in the state of Rondonia within the Amazon region. The site is forested and is one of the Reference Sites of the Large-Scale Biosphere-Atmosphere Experiment in the Amazon Basin (LBA) Continental-Scale Experiment (CSE). Time series and mean diurnal cycles of precipitation, near-surface temperature, latent and sensible heat fluxes, surface incoming shortwave and net radiation fluxes are shown for 24-h and 48-h forecasts. In the global model, the predicted incoming shortwave radiation and net radiation are similar to observed values; however, this is accompanied by large overestimate of deep clouds and precipitation. Partition of the available energy results in an overestimate of the sensible heat fluxes and an underestimate of the latent heat fluxes. The latent heat fluxes are large shortly after rain, but decay quickly. No clear improvement is noted in the 48-h forecasts compared with the 24-h forecasts.
    The Eta Model is a grid-point limited-area model. Its precipitation forecasts are similar to observations; however, the model overestimates the incoming shortwave radiation, resulting in excessive net radiation. The Eta sensible and latent heat fluxes are both overestimated, and 48-h forecasts produce small improvements over the 24-h forecasts. Near-surface temperatures are overestimated by both models. The global model requires a reduction in precipitation production, and both models require a reduction in incoming short-wave radiation at the surface.
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  • Sean F. MILTON, P. EARNSHAW
    Volume 85A (2007) Pages 43-72
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    Components of the surface water and energy balance are evaluated in the Met Office global Numerical Weather Prediction (NWP) 00-36 hour forecasts using (i) GEWEX Continental Scale Experiment (CSE) reference site data provided by the Coordinated Enhanced Observing Period (CEOP) project and (ii) other earth observing datasets from satellites and in-situ measurements. The global hydrological cycle in the model is in reasonable balance in recent model versions. However, comparison against available observations suggest that both precipitation and evaporation are overestimated over both land and ocean, with largest errors over the tropical oceans. Comparison of the model's seasonal and diurnal cycles of surface fluxes, temperature, precipitation, and moisture against the GEWEX/CEOP CSE sites during October 2002 to September 2003 reveals several issues concerning model parametrization performance. For the high latitude (Arctic) sites low cloud is overestimated during boreal winter leading to an enhanced greenhouse effect and too warm near surface temperatures in the model. Snow melt occurs too early in boreal spring in the model forecasts which currently have no snow analysis component. Possible reasons for early snow melt are discussed including the specification of albedo over heterogeneous terrain and excessive sublimation of snow in the model. The mid-latitude CEOP sites all show excessive evaporation and precipitation during boreal spring and early summer and comparison with the International Satellite Cloud Climatology (ISCCP) products show systematic under prediction of cloud cover over mid-latitude land in summer. Some of the largest biases in mid-latitude surface fluxes in summer are during daytime on non-precipitating cloudy days where the model overestimates the downward SW radiation, latent and sensible heat fluxes. Finally, over tropical land we see a tendency to underestimate precipitation which is in direct contrast to tropical oceans where precipitation accumulations are too large. We have also used the CEOP data to investigate structural errors in the vertical profiles of tropical humidity which suggest deficiencies in the convection scheme.
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  • Lawrie RIKUS
    Volume 85A (2007) Pages 73-97
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    The Coordinated Enhanced Observing Period (CEOP) Project has initiated the collection of model output location time series (MOLTS) data from numerical weather prediction and assimilation centers, including the Australian Bureau of Meteorology. These were designed to complement the collection of in situ observational data sets at the same 41 locations. This study is a preliminary attempt to assess the differences and similarities between the MOLTS and time series of the in-situ data. The MOLTS from the Bureau’s global model for a number of atmospheric surface variables are compared with in-situ data for 6 locations for the entire year of EOP3 (October 2002 to September 2003). Using surface pressure as a prototype a number of preliminary comparisons of different properties of the two types of data are performed. The model fields from the 6 hour assimilation forecast series and from the concatenated 12 to 36 hour forecasts are first compared with hourly in-situ observations in simple gross terms; simple statistics and scatter plots have been obtained to identify areas for further investigation. Global wavelet power spectra are compared to show the behavior of the dominant modes of variability and the average annual diurnal variations of the variables are derived. Some case studies with other variables with increasing sensitivity to sub-grid scales and increasing dependency on surface properties are then documented. The model and in-situ time series show similar behavior for surface pressure with greater differences for the other variables. Precipitation shows the greatest differences.
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  • Kun YANG, Mohamed RASMY, Surendra RAUNIYAR, Toshio KOIKE, Kenji TANIGU ...
    Volume 85A (2007) Pages 99-116
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    Using data archived in the Coordinated Enhanced Observing Period (CEOP) project, this study presents an initial evaluation of the prediction skill of five General Circulation Models (GCMs) and three Land Surface Models (LSMs). Comparisons between observations and the GCMs show that all the models are able to produce an afternoon peak in precipitation, but other major features are not well produced, including the total amount of precipitation, onset time of the afternoon peak, the early-evening low (around 1800 LST), and the partition between convective and stratiform rainfall. The ratios of evaporation to precipitation differ among the GCMs. Evaporation in some of the GCMs is even greater than precipitation, perhaps due to the model spin-up effect. In terms of the surface radiation budget, the GCMs generally over-predict downward shortwave radiation and under-predict downward longwave radiation; further investigations of the causes of these trends require cloudiness observations. In terms of the surface energy budget, the GCMs generally over-predict nighttime downward sensible heat fluxes and under-predict diurnal ranges of surface-air temperature difference, as heat transfer resistances are under-predicted. Finally, three offline LSMs driven by identical forcing are evaluated, and we note that the reproduction of surface temperature is not a suflicient condition for a LSM to reproduce surface energy partition.
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  • Alex C. RUANE, John O. ROADS
    Volume 85A (2007) Pages 117-143
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    The Continental United States summertime diurnal surface and column-integrated atmospheric water and energy components are compared among three reanalyses. The strengtJh of the diurnal solar forcing leads to consistent phases among surface energy components across the continent and all reanalyses, but the amplitudes vary widely. This forcing has a particularly strong and direct impact on the surface energy cycle, but interacts with many aspects of the surface and column-integrated water and energy cycles through dynamical convergence, leading to large diurnal fluctuations in the atmospheric reservoir of water vapor and total dry energy. Although they are negligible on timescales greater than a year, the tendency terms of the water and energy budgets at the surface and in the atmosphere are important on the diurnal scale. The North American Regional Reanalysis (NARR) displays a diurnal circulation pattern centered over Northern Texas that links together regional patterns in the diurnal cycles of assimilated precipitation. Constructed vapor flux convergences from the National Centers for Environmental Prediction/Department of Energy (NCEP/DOE) Reanalysis-2 Global Spectral Model and the Experimental Climate Prediction Center’s reanalysis using an updated Seasonal Forecast Model reproduce many of the observed regional circulation and convergence patterns, but fail to generate the appropriate diurnal precipitation, presumably due to inadequate convective parameterizations. Diurnal variations in atmospheric energy respond not only to the direct solar forcing, but also to the resulting dynamically-forcedsemidiurnal thermal tide.
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  • Insa MEINKE, J. ROADS, M. KANAMITSU
    Volume 85A (2007) Pages 145-166
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    Precipitation simulated using the Regional Spectral Model (RSM) during the Coordinated Enhanced Observing Period (CEOP; July 1, 2001 to December 31, 2004) is evaluated by transferring the RSM to seven different regions of the globe and comparing the simulations with observations. These regions cover the eight Continental-Scale Experiments (CSEs) of the Global Energy and Water-cycle EXperiment (GEWEX) and encompass a broad variety of physical and dynamical meteorological processes. Gridded observations of the Global Precipitation Climatology Project (GPCP) and the Global Precipitation Climatology Center (GPCC), as well as CEOP reference site precipitation observations are compared with the RSM simulated precipitation for the first half of the CEOP Enhanced Observation Period (EOP) III (October 2002 to March 2003). After estimating the uncertainty ranges of both the model and the observations, model deficiencies were obtained for almost all model domains in terms of the amount of simulated precipitation. Although the RSM is able to accurately simulate the seasonal evolution and spatial distribution of precipitation, the RSM has an almost uniform positive bias (i.e., RSM values are greater than observed values) over almost all the domains. Most of the positive bias is associated with convection in the Intertropical Convergence Zone (ITCZ) or monsoonal convection in Southeast Asia. Predicted stratiform precipitation is also excessive over areas ofelevated topography. As the control simulations used a Relaxed Arakawa-Schubert scheme (RAS), sensitivity tests with three additional convection schemes were then carried out to assess whether the simulations could be improved. The additional convection schemes were: 1) the Simplified Arakawa-Schubert scheme (SAS); 2) the Kain-Fritsch scheme (KF); and 3) the National Centers for Atmospheric Research (NCAR) Community Climate Model (CCM) scheme. The precipitation simulation was significantly improved for almost all domains when using either the KF scheme or the SAS scheme. The best simulations of ITCZ convective precipitation and Southeast Asian monsoon convective precipitation were achieved using the SAS convection scheme.
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  • Kit K. SZETO
    Volume 85A (2007) Pages 167-186
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    The Saskatchewan River Basin (SRB) in Canada is one of the most important agricultural regions for the country. Despite the critical dependency of the region’s agricultural and societal activities to climate variability and change, no comprehensive water and energy budget assessment has yet been developed for this drought-prone region. This study represents the first attempt at developing a comprehensive climatology of water and energy budgets for the SRB. Different observed, remotely-sensed, (re-)analyzed and modeled datasets were used to obtain independent estimates of the budgets. In panicular, flux measurements from the Boreal Ecosystem Research and Monitoring Sites (BERMS) Coordinated Enhanced Observing Period (CEOP) reference site provide valuable validation data for the surface flux assessments. Budget results for the SRB are compared to those assessed for the Mackenzie River Basin to gain insights into the differences in water and energy cycling, and challenges in their quantifications, for these two neighboring major basins in North America. Apart from the development of state-of-the-art budget estimates for the SRB, the relative merits of current models, data assimilation systems and global blended datasets in representing aspects of the water and energy cycle of this semi-arid region were also assessed. Although some of the assessed component budgets compared quite well with observations, magnitudes of the residuals in balancing the budgets are often comparable to the budget terms themselves in all the analysis datasets, suggesting that substantial improvements to the models and observations are needed before we can vastly improve the assessment of water and energy budgets for the regron.
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  • Hiroko KATO, Matthew RODELL, Frank BEYRICH, Helen CLEUGH, Eva van GORS ...
    Volume 85A (2007) Pages 187-204
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    Numerical land surface models (LSMs) are abundant and in many cases highly sophisticated, yet their output has not converged towards a consensus depiction of reality. Addressing this matter is complicated by the huge number of possible combinations of input land characteristics, forcings, and physics packages available. The Global Land Data Assimilation System (GLDAS) and its sister project the Land Information System (LIS) have made it straightforward to test a variety of configurations with multiple LSMs. In order to compare the impacts of the choice of LSM, land cover, soil, and elevation information, and precipitation and downward radiation forcing datasets on simulated evapotranspiration, sensible heat flux, and top layer soil moisture, a set of experiments was designed which made use of high quality, physically coherent, 1-year datasets from four reference sites of the Coordinated Enhanced Observing Period (CEOP) initiative. As in previous studies, it was shown that the LSM itself is generally the most important factor governing output. Beyond that, evapotranspiration seems to be most sensitive to precipitation, land cover, and radiation (in that order); sensible heat flux is most sensitive to radiation, precipitation, and land cover; and soil moisture is most sensitive to precipitation, soil, and land cover. Various seasonal and model specific dependencies and other caveats are discussed. Output fields were also compared with observations in order to test whether the LSMs are capable of simulating an observed reality given a plausible set of inputs. In general, that potential was fair for evapotranspiration, good for sensible heat flux but problematic given its strong sensitivity to the inputs, and poor for soil moisture. The results emphasize that improving the LSMs themselves, and notjust the inputs, will be essential if we hope to model land surface water and energy processes accurately.
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  • Michael G. BOSILOVICH, Jon D. RADAKOVICH, Arlindo da SILVA, Ricardo TO ...
    Volume 85A (2007) Pages 205-228
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    In an initial investigation, remotely sensed surface temperature is assimilated into a coupled atmosphere/land global data assimilation system, with explicit accounting for biases in the model state. In this scheme, a incremental bias correction term is introduced in the model’s surface energy budget. In its simplest form, the algorithm estimates and corrects a constant time mean bias for each gridpoint; additional benefits are attained with a refined version of the algorithm which allows for a correction of the mean diurnal cycle. The method is validated against the assimilated observations, as well as independent near-surface air temperature observations. In many regions, not accounting for the diurnal cycle of bias caused degradation of the diurnal amplitude of background model air temperature. Energy fluxes collected through the Coordinated Enhanced Observing Period (CEOP) are used to more closely inspect the surface energy budget. In general, sensible heat flux is improved with the surface temperature assimilation, and two stations show a reduction of bias by as much as 30 W m−2. At the Rondonia station in Amazonia, the Bowen ratio changes direction in an improvement related to the temperature assimilation. However, at many stations the monthly latent heat flux bias is slightly increased. These results show the impact of univariate assimilation of surface temperature observations on the surface energy budget, and suggest the need for multivariate land data assimilation. The results also show the need for independent validation data, especially flux stations in varied climate regimes.
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  • Kun YANG, Takahiro WATANABE, Toshio KOIKE, Xin LI, Hideyuki FUJII, Kat ...
    Volume 85A (2007) Pages 229-242
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    Low-frequency microwave brightness temperature is strongly affected by near-surface soil moisture; therefore, it can be assimilated into a land surface model to improve modeling of soil moisture and the surface energy budget. This study presents a new variational land system used to assimilate AMSR-E brightness temperature of vertical polarization of 6.9 GHz and 18.7 GHz. The system consists of a land surface model (LSM) used to calculate surface fluxes and soil moisture, a radiative transfer model (RTM) to estimate the microwave brightness temperature, and an optimization scheme to search for optimal values of soil moisture by minimizing the difference between modeled and observed brightness temperature. The LSM is an improved simple biosphere model for sparse vegetation modeling and the RTM is a Q-h model that can account for the effects of surface roughness and vegetation. Several parameters in the LSM and RTM can significantly affect the outputs of the land data assimilation system but their values are either highly variable or unavailable. To solve this problem, we developed a dual-pass assimilation technique. Pass 1 inversely estimates the optimal values of the model parameters with long-term (∼months) forcing data and brightness temperature data, while Pass 2 estimates the near-surface soil moisture in a daily assimilation cycle. This system is driven by well-established reanalysis data and global data sets of leaf area index, precipitation, and surface radiation, and was tested at a CEOP (Coordinate Enhanced Observing Period) reference site on the Tibetan Plateau. The system not only detected the effect of precipitation events that were missing in the forcing data, but also led to a significant improvement in modeling of the surface energy budget.
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  • Pathmathevan MAHADEVAN, Toshio KOIKE, Hideyuki FUJII, Katsunori TAMAGA ...
    Volume 85A (2007) Pages 243-260
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    At climatic time-scales, soil moisture is one of the most important boundary condition controlling fluxes to the atmosphere. Here, we explore the feasibility of synthesizing distributed fields of soil moisture using AMSR-E observations and a novel application of data assimilation within a hydrological model. We modified our existing Land Data Assimilation Scheme (LDAS) by specifically considering: (1) weak constraint assumptions rather than a strong constraint, thus accounting for the existence of model errors; and (2) the effects of volume scattering within the soil medium in the Radiative Transfer Model (RTM). Adopting the “effects of volume scattering within the dry soil medium” in the RTM is a new step for satellite-based data assimilation techniques for the retrieval of soil moisture.
    This LDAS can be used to assess model parameters and estimate vertical profiles of soil moisture, especially in very dry regions (volumetric soil moisture is equal to or less than 5-15%) as well as soil-surface and canopy temperatures by comparing passive microwave observations using a unique minimization technique termed Very Fast Simulated Annealing (VFSA). To validate our new LDAS, AMSR-E observations, gathered in Mongolia, were assimilated into the Land Surface Model (LSM) via the modified RTM. Observed micrometeorology boundary conditions for Mongolia were drawn from the CEOP database. In studies that simulate 2-week dry periods, the results of the revised LDAS are in better agreement with observational data than the results of open-loop simulations.
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  • Tsutomu YAMANAKA, Ichirow KAIHOTSU, Dambaravjaa OYUNBAATAR, Tseveenchi ...
    Volume 85A (2007) Pages 261-270
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    In this study, we monitored the surface soil moisture at 15 locations within an area of 100 km × 100 km in the Mongolian steppe region. A principal component analysis was used to determine the characteristics and dominant patterns of spatiotemporal variations in the measured surface soil moisture. The results reveal that the predominant pattern of temporal variation is related to large-scale rainfall and that this was spatially uniform over the entire study area. In terms of both temporal and spatial patterns, the spatial heterogeneity of rainfall activity was a minor factor, accounting for less than 33% of the total observed variance. The most dominant pattern in the spatial distribution of surface soil moisture showed a correlation with the spatial distribution of the mean or minimum water content, and the minimum water content was largely equivalent to the wilting point, which is a soil-hydraulic index. Thus, we conclude that the most dominant pattern of surface soil moisture distribution over the study region is regulated by soil-hydraulic properties. Rainfall events acted to disturb or reset this pattern, but the pattern was re-established during drying of the soil.
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  • Kenji TANIGUCHI, Toshio KOIKE
    Volume 85A (2007) Pages 271-294
    Released: March 30, 2007
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    In the spring of 2004, we implemented intensive field observations in the eastern part of the Tibetan Plateau. In this study, we use the field observation data, as well as satellite observation data and reanalysis data, to examine increases in diurnal potential temperature and variations in atmospheric conditions over the eastern part of the Tibetan Plateau. The results of intensive radiosonde observations reveal a significant temperature increase attaining to the tropopause in April. The depth of the mixing layer, estimated from the vertical profile of potential temperatures, was much smaller than the height of the temperature increase. This result indicates that the temperature rise was not solely caused by thermally induced dry convection. During the observation period, strong cloud activity was observed. Cloud-top heights derived from GOES-9 and radiosonde observations indicate that active cumulus convection coincides with the temperature rise in the upper troposphere. For small increases in temperature, lower cloud-top heights are observed.
    Numerical simulations were also conducted using a regional atmospheric circulation model and radiosonde observation data as initial conditions. The results of the numerical simulations with wet and dry conditions and ideal wind direction (no meridional wind component) reveal that in the wet case air is more efficiently warmed in the upper troposphere with cloud activity. By introducing the observed wind direction as an initial condition, the simulation predicts strong cloud convection over a wide region of the model domain and a greater increase in potential temperature; this result is comparable to observed data.
    In previous studies, sensitive heat transfer by thermally induced dry convection was thought to be the main cause of pre-monsoon atmospheric heating over the Tibetan Plateau; however, the results of the observation analysis and numerical simulations described in the present study suggest that strong cloud convection plays an important role, even during the period prior to the rainy season.
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  • Yaoming MA, Minhong SONG, Hirohiko ISHIKAWA, Kun YANG, Toshio KOIKE, L ...
    Volume 85A (2007) Pages 295-309
    Released: March 30, 2007
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    This study proposed a parameterization methodology based on Landsat-7 ETM data and field observations and tested it for deriving an evaporative fraction (EF) over a heterogeneous landscape. As a case study, the methodology was applied to the experimental area of CAMP/Tibet located on the central Tibetan Plateau. Four scenes of Landsat-7 ETM data were used in the study. Scenes of 9 June 2002 and 28 August 2002 were selected as case examples of summer and autumn, respectively; the scene of 2 December 2002 was selected as a winter case; and 24 March 2003 was selected as a spring case (or pre-monsoon period). To validate the proposed methodology, the Landsat-7 ETM derived EFs were compared to ground-measured values in four different months that spanned a wide range of surface conditions and surface features. This comparison revealed that the predictions were in good accordance with the ground measurements with absolute percent differences of less than 9.5%. It was concluded that the proposed methodology successfu11y facilitates the retrieval of EF using Landsat-7 ETM data and field observations over the study area.
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  • Xiangde XU, Xiaohui SHI, Lian XIE, Yafei WANG
    Volume 85A (2007) Pages 311-323
    Released: March 30, 2007
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    This study investigates the consistency of interdecadal variations in the East Asian summer monsoon (EASM) and changes in the heterogeneous structure of sealland springtime surface air temperature (SAT) over eastern China and the adjacent ocean (including the South China Sea and part of the Western Pacific Ocean). A profile of the summer mean meridional wind over eastern China for the past 40 years shows a coherent interdecadal weakening trend for the EASM. The decadal-scale (11-year running mean) summertime (June-August) wind and springtime (March-May) SAT fields are decomposed using the empirical orthogonal function (EOF) method. The results indicate that both the leading eigen-vector of the decadal-scale meridional wind and that for the SAT over East Asia account for more than 70% of the total variance. Their time coefiicients show a similar trend, with the transition from negative to positive values occurring around 1978; i.e., the EASM turned from a stronger phase to a weaker phase around 1978. The springtime sealland SAT distribution before and after 1978 also showed a shift in interdecadal trends. Therefore, the south-lowlnorth-high nature of the principal component of springtime SAT over eastern China is closely related to the progressive weakening of the EASM. Our results suggest that within the context of the regional impact of global climate change, heterogeneous changes in the regional springtime sea/land SAT in eastern Asia might in part have led to a weakening of the effect of sealland thermal driving on the EASM.
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  • B.K. BASU, G. IYENGAR
    Volume 85A (2007) Pages 325-336
    Released: March 30, 2007
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    The observed and the model forecast rainfall and other atmospheric fields are compared to determine the skill of the National Centre for Medium Range Weather Forecasting (NCMRWF) model in forecasting precipitation and circulation features over India, we compared observed and forecast rainfall and other atmospheric fields for the boreal summer monsoon season of 2004. This season was an important period within the period 4 of the Coordinated Enhanced Observing Period (CEOP). For comparison of observed rainfall with predicted values, station values are averaged over the area represented by each grid point of the model. For other fields, comparisons were made between the analysis and forecast values at the same horizontal resolution. The model showed considerable skill in predicting the daily and seasonal accumulated rainfall amounts when averaged over the whole of India. The predicted all-India average precipitation tends to increase in magnitude with increasing forecast period. The model forecasts that were undertaken especially for the CEOP project reproduced the important features of the summer monsoon over India. The onset of monsoon is captured in terms of both the convective precipitation and diabatic heating fields forecast by the model. Variations in monsoon activity between July and August are also well simulated in the monthly averaged forecast fields for these two months.
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  • Sen CHIAO, Ana P. BARROS
    Volume 85A (2007) Pages 337-361
    Released: March 30, 2007
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    This objective of this study is to elucidate the processes that govern the space-time persistence of the hydrometeorological dryline in Northwest India. The working hypothesis is that orographic forcing and land-atmosphere interactions via soil moisture and vegetation processes lock the hydrometeorological line to the Aravalli range and the Thar Desert (a.k.a. the Great Indian Desert). For this purpose, simulations of active and break phases of the 2001 monsoon season were conducted using a mesoscale model (MM5). During the active phases of the monsoon, southeasterly depressions from the Bay of Bengal propagate over northern India, maintaining sustained convergence of moist available energy east of the Aravalli range, leading to increased rainfall and cloudiness patterns consistent with deep convective activity. Drier air originating from the Arabian Sea in the Western Indian Ocean is constrained to the west. During monsoon break phases, moisture convergence from the Bay of Bengal to the Northern India Convergence Zone (NICZ) decreases dramatically, weakening regional circulations east of the Aravalli range. This allows ventilation of the central portion of the NICZ through penetration of westerly dry air, leading to reduced rainfall, lower soil wetness, decrease of latent heat fluxes, and finally lower CAPE and humidity in the lower troposphere. Whereas the inland propagation of monsoon depressions from the Bay of Bengal triggers the onset (demise) of active and break periods, the sustainability of either regime requires strong feedbacks between humidity and stability in the lower troposphere and the surface energy balance: negative in the case of monsoon breaks, positive in the case of active periods. This study shows that, albeit relatively modest (<600 m average elevation), the Aravalli provides sufiicient lift (upwind) and descend (downwind) to organize the spatial distribution of updrafts westward (active phase) and eastward (break phase) of the topographic divide in such a way that low level updrafts are nearly suppressed over the Thar Desert. Sensitivity experiments with modified soil and vegetation cover show that daytime latent heat fluxes (and evapotranspiration) play an important role in the spatial orgnization of CAPE and in triggering light rainfall processes in the semi-arid regions of northwest India, whereas the occurrence of heavy rainfall to the east of the Aravalli range is controlled by large-scale monsoon dynamics.
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  • Weiping LI, Yongkang XUE, Isabelle POCCARD
    Volume 85A (2007) Pages 363-383
    Released: March 30, 2007
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    The climate impacts of leaf area index (LAI) and fractional vegetation cover (FVC) on the West African summer monsoon in 1987 and 1988 were investigated through a series of numerical experiments conducted with satellite products and the Simplified Simple Biosphere land surface model (SSiB). The SSiB was run in the offIine mode as well as in the coupled mode with the National Centers for Environmental Prediction General Circulation Model (GCM). Prescribed monthly LAI and FVC from a look-up table based on limited ground surveys and those derived from satellite remote sensing were employed in the control and test runs, respectively.
    Compared with the control runs, both the GCM and offline test runs with satellite measured LAI/FVC produce higher soil moisture and lower surface temperature in tropical West Africa to the south of about 15°N, with the maximum deviations being located around 12°N. This leads to the northward shift of the maximum of positive latitudinal temperature gradient. The associated easterly shear in the lower troposphere results in the African easterly jet and summer rainfall band in West Africa shifting to the north, which partially corrects the dry bias in the GCM control runs. In addition, the GCM test run simulates a relatively stronger West African summer monsoon in 1988, with a northward shifted African easterlyjet, a stronger tropical easterlyjet, and more rainfall than in 1987, consistent with observations. However, due to small differences in satellite measured LAI/FVC between 1987 and 1988, the model fails to produce interannual variations of precipitation as large as seen in the observation. Water balance analysis has also been carried out to investigate the dominant processes affecting the changes in precipitation. The relative contributions of moisture flux convergence and surface evapotranspiration are identified. The comparisons between GCM and offline results in this study demonstrate a possible future application of CEOP data in African climate study.
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  • Hsi-Yen MA, C. Roberto MECHOSO
    Volume 85A (2007) Pages 385-401
    Released: March 30, 2007
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    In this study, we examine the South American Monsoon System (SAMS) variability with an emphasis on three-day periods or longer during which time the low-level wind in central Amazonia is consistently from the west or the east (westerly and easterly wind regimes, WWRs and EWRs, respectively). We use observational and Reanalysis datasets for the southern summer, as in previous studies on SAMS variability. Our research methodology involves the addition of model data that consists of the Coordinated Enhanced Observing Period (CEOP) Model Output Location Time Series (MOLTS) at locations in the SAMS region, and ensemble atmospheric general circulation model (AGCM) simulations of the southernsummer season.
    For both wind regimes, the observed and simulated composites of anomalous precipitation over South America show a dipole pattern with poles in northwestern and central-southeastern Brazil. During WWRs (EWRs), precipitation anomalies at the central-southeastern pole are positive (negative), indicating a stronger (weaker) SACZ. In addition, during WWRs the upper-level monsoon high is stronger and the subtropical jet in the South American sector is stronger and closer to the equator.
    We also examine the diurnal cycle of rainfall from three CEOP MOLTS for Rondonia and Brasilia, which are situated at different poles of the rainfall anomalies dipole. The diurnal cycle in precipitation during both wind regimes shows an early-afternoon maximum at the selected locations. At Rondonia (Brasilia), there is a second early-morning (nocturnal) maximum on EWR (WWR) days. The diurnal mean precipitation in the regime that shows this maximum value, which is primarily due to enhanced cumulus convection, is higher than that in the other regime. In the simulation, WWRs and EWRs occur with approximately equal frequency. There is also a dipole pattern in anomalous precipitation during the days of each regime, although the poles are displaced relative to the observations. The simulated diurnal cycles of rainfall for the different wind regimes are nearly identical. Possible explanations for these AGCM difficulties are briefly discussed.
    Lag composites of geopotential height anomalies at 700 mb prior to the establishment of the wind regimes in Amazonia show the development of structures in the South Pacific that resemble the principal modes of variability in that region. This indicates the existence of links between the wind regimes and the modes of intraseasonal variability over South America. It is proposed that the wind regimes are associated with low-frequency variability in the extratropical circulation.
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  • William K.M. LAU, Kyu-Myong KIM, Myong-In LEE
    Volume 85A (2007) Pages 403-416
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    In this paper, we characterize the climatological diurnal cycles over monsoon land and ocean regions, and seasonal cycles for six major monsoon systems around the world, from observations and outputs of the NASA Seasonal-to-Interannual Prediction Project (NSIPP) general circulation model outputs. Over monsoon land regions, the diurnal cycle has a pronounced late afternoon peak in rainfall and over the oceans a much weak diurnal signal with an early morning peak. The NSIPP model produces a daily peak in rainfall about 2-3 hours earlier than observed, possibly attributed to a cumulus parameterization which does not include cloud life cycle effects, and which lack detailed treatment of boundary layer processes. The seasonal cycles of all monsoon rain systems are controlled by an ITCZ and a subtropical and/or extratropical component due to the presence of contiguous large continental land mass. Strong climatological intraseasonal oscillations (CISO) are found in the monsoon systems of South Asia and East Asia, Australia, and South America, and to a lesser degree for West Africa and Mexico/North America. The NSIPP model captures the slow component seasonal component reasonably well, but the CISO’s are not well simulated.
    Analysis with reference to a new monsoon index shows that the major monsoon systems can be classified into three major groups (M1-3) according to the relative strength of continental vs. oceanic controls. East Asian and South Asian monsoons belong to a group (M1), where the continental influence is stronger than that from the ITCZ. The North America and South America monsoons show similar characteristics with the ITCZ influence slight stronger than continental influence (M2). The West Africa and Australia monsoons are found to be essentially ITCZ-monsoon systems (M3), with strong oceanic control, and limited poleward excursion of the monsoon rainbelt. We also find a clear trend associated with an increase in continentality for M3 monsoons, i.e., the West African and the Australian monsoons in the last two decades. We speculate that the former is linked to the partially recovery of the Sahel drought since the 1980’s.
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  • Hiroyuki TSUTSUI, Toshio KOIKE, Tobias GRAF
    Volume 85A (2007) Pages 417-438
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    This paper presents a snow algorithm for the Advanced Microwave Scanning Radiometer (AMSR)and the AMSR for the Earth Observation System (AMSR-E). We validate the algorithm using snow-depth data recorded at the Coordinated Enhanced Observing Period (CEOP) Reference Site in Yakutsk, Russia. A new radiative transfer model for layered snow is developed by combining the 4-stream fast model and the dense media radiative model (DMRM); this model is then introduced into the new algorithm. The algorithm considers the effects of land-surface hydrological conditions under the snow layer and snow-panicle grain size on brightness temperatures in the microwave region by using the multi-frequency channels of AMSR and AMSR-E. The algorithm was validated at seven snow-measurement points within the CEOP Reference Site in Yakutsk from October 2002 to March 2003, corresponding to the first half of the third Enhanced Observing Period (EOP3).
    We calculated the root mean square error (RMSE) based on the error between observed and estimated values and calculated the residual standard deviation (RSD) for all verification periods. We also calculated the proportion and RMSE of overestimated and underestimated values. The average RMSE is low (4.0 cm) and the average RSD is 2.8, indicating only minor variation. In addition, 56% of values were overestimated, and the average RMSE of the overestimated values was 3.9 cm; the average RMSE for the 44% of values that were underestimated was 2.4 cm. Accordingly, the estimated snow depth is in relatively good agreement with in situ data.
    For the analyses undertaken at each site, we used the proposed algorithm to assess the influence of forest cover, frozen soil, and cloud cover on the process of estimating snow depth. We propose that such analyses are necessary when estimating snow depth.
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  • Hongbo SU, E.F. WOOD, M.F. MCCABE, Z. SU
    Volume 85A (2007) Pages 439-459
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    In this paper, the Coordinated Enhanced Observing Period (CEOP) data during an Enhanced Observing Period (EOP-1) is used to assess the Surface Energy Balance System (SEBS) model. The purpose of this study is to evaluate the adaptability of SEBS to different climatic zones and land cover classifications at two different scales. The SEBS model was examined at the field (tower) scale based primarily on in-situ observations from CEOP sites. To examine a broader scale application, remotely sensed land surface temperature (LST) from the MODIS sensor and surface meteorology from the Global Land Data Assimilation System (GLDAS) were used for the required forcing datasets. Comparisons at tower scale show that the model predictions of the energy fluxes agree reasonably well with the observations. The root mean square error (RMSE) of the ET prediction based on MODIS Land Surface Temperature (LST) plus CEOP meteorological observations is about 61 W m−2 at a grassland site (Cabauw) and a needle leaf forest site (BERMS). The RMSE of ET predication at a corn site (Bondvi11e) is 96 W m−2 and the corresponding percentage error is 28.9%. When GLDAS forcing was used instead of the CEOP tower observations, the RMSEs of ET prediction at Cabauw, BERMS and Bondvi11e are increased to 82, 84 and 140 W m−2 respectively. The negative bias of surface downward radiative forcing from GLDAS contributed much to the larger deviation of the ET prediction when compared to tower based values. The innovative aspects of our study in this paper are: a) No similar work on evaluating remote sensing based ET model under a diverse climate and land cover condition has been done before; b) ET modeling was assessed in different scales ranging from site scale to GLDAS grid cell; c) The framework of estimating the spatial distribution of ET combining satellite data and available ground meteorology is tested.
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  • Eiji IKOMA, Katsunori TAMAGAWA, Tetsu OHTA, Toshio KOIKE, Masaru KITSU ...
    Volume 85A (2007) Pages 461-473
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    With the recent advances in observation technologies has come a dramatic increase in the amount of Earth environmental data. However, data obtained through sensors often contains a great deal of errors and noise due to system instabilities and related issues. The labor costs to remove such noise and to maintain the quality of the data has become an important issue.
    In this paper, we propose a web-based quality assurance system through which the person responsible for the observing system can easily check whether the sensed data are reasonable or not, and can add various kinds of flags to items of data.
    The system we developed has actually been used by several investigators at a number of reference sites that are part of the Coordinated Enhanced Observing Period (CEOP) network ofground truth locations. These users have reported that data quality checking can be done much more efficiently with our system than by other methods. The system is able to simultaneously show various kinds of sensor data so that users can easily check inter-correlations. This correlation assisted quality checking mechanism has proven to be quite effective. There are also many other capabilities that are detailed here. QUASUR-1 was used for the first half of Enhanced Observing Period 3 (October 2002-March 2003) and QUASUR-2 is currently being applied to data collected during the second half of EOP3 (April 2003-September 2003).
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  • Frank TOUSSAINT, Michael LAUTENSCHLAGER, Hans LUTHARDT
    Volume 85A (2007) Pages 475-485
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    The World Data Center for Climate (WDC-Climate) is hosted at the Max Planck Institute for Meteorology (MPI-M) in Hamburg, Germany. WDC-Climate stores global and regional model output for the CEOP project, and raw model output is available in a number of different data structures. This model output is currently being restructured into a more homogenous form. This paper provides an overview of the CEOP model output and its overall data structure at WDC-Climate, as well as the different ways that this output can be accessed.
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  • Rong XIE, Ryosuke SHIBASAKI, Masafumi ONO
    Volume 85A (2007) Pages 487-517
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    CEOP (Coordinated Enhanced Observing Period) is currently establishing an integrated global observation system for the water and energy cycles to meet both scientific and social needs. To integrate various CEOP data such as satellite products, reference site data, and model output such as Model Output Location Time Series (MOLTS), it is necessary to exactly represent or reconstruct the geometric conditions involved in observing or acquiring the data via space-borne sensors etc. Information that contains a description or reconstruction of the observation conditions is usually represented by metadata. The standardization of metadata and imagery metadata is being undertaken by several international organizations, including ISO/TC 211. This paper reviews the present status of documents that contain metadata specifications and proposes the CEOP/ISO metadata model for the development of standardized metadata to fulfill the requirements of integrating CEOP data and to conform to metadata standards. The results are developed and presented in terms of satellite metadata, reference-site metadata, and MOLTS metadata. We also present the metadata application architecture that describes how to use these metadata to establish a data service and data discovery on a local or wide-area network for the integration of satellite observation data.
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  • Benjamin BURFORD, Osamu OCHIAI, Yonsook ENLOE, Ken MCDONALD
    Volume 85A (2007) Pages 519-527
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    The Coordinated Enhanced Observing Period (CEOP) is an initial step towards establishing an integrated observation system for the global water cycle, bringing together the capabilities of both satellite based and ground based (remote and in-situ) observing systems. The CEOP program initiated a discussion with the Committee on Earth Observation Satellites (CEOS) Working Group on Information Systems and Services (WGISS) for assistance in the development of advanced tools for integrated access, visualization and comparison of the multiple types of data being gathered by the CEOP project. CEOS WGISS initiated a project to collaboratively prototype a set of tools and services needed to provide user-friendly, efficient and effective integrated access to the CEOP (insitu, satellite and model output) data to support global water cycle research. The design and development of the prototypes in the WGISS Test Facility for CEOP, including its current capabilities and planned future developments, are presented here.
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  • Toshihiro NEMOTO, Toshio KOIKE, Masaru KITSUREGAWA
    Volume 85A (2007) Pages 529-543
    Released: March 30, 2007
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    A large amount of data is being collected and archived in the Coordinated Enhanced Observing Period (CEOP) project to help to increase researchers’ understanding and knowledge of the global water cycle system. We describe the data archive system that integrates data (in-situ, satellite, and model output) produced by the CEOP project. We also detail the user interface for analyzing the data. First, we explain the characteristics of the global water cycle data to be archived and the functions requested by users to analyze the data. We then explain the architecture of the archiving system and its graphical user interface (GUI) that we are currently constructing. The interface will integrate data of various dimensions, temporal and spatial resolutions, coordinates, precision, and format. This interface will provide users with the environment to handle data irrespective of type.
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  • Eiji IKOMA, Masaru KITSUREGAWA, Kenji TANIGUCHI, Toshio KOIKE
    Volume 85A (2007) Pages 545-559
    Released: March 30, 2007
    JOURNALS FREE ACCESS
    A large display space potentially improves data exploration, especially when where there are several types of data sets to control. To better understand the feasibility of a large display space, we implemented a display wall assisted visual mining system. A 5 m × 2.5 m display allows users to simultaneously visualize various types of data. The system also has a very high resolution of 15 XGA displays (each XGA display has 1024 pixel × 768 pixel resolution). With these attributes, the user can easily examine and visualize a dense data set in detail. To our knowledge, few systems of this type that are easy to use have been realized. A number of systems are now functional (e.g., the NASA AMES Hyperwall, http://www.nas.nasa.gov/Groupsl/VisTech/hyperwall/). However, these systems require much knowledge and power of the user. Most users of such systems have to use some special application, which can be difficult for earth environmental researchers. Although the proposed system has had limited testing by some researchers, we believe that our experience would be helpfu1 for users who are trying to develop similar systems. The proposed system is more efficient as it allows for simultaneous multi-dimensional visualization of complex data products, and various mining functions, such as two-dimensional correlation, are also prepared for the Coordinated Enhanced Observing Period (CEOP) data archive. By using these functions, various advanced analyses that are not easily utilized with conventional mining tools are attained. Moreover, several scenarios using the powerful capability of this tool are also presented. Finally, the process of data analysis in the proposed system becomes much more efficient through the use of a large-scale high-resolution display wall.
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