Possible changes of life zone distribution in reaction to global climate change in northeast China were simulated based on climate-vegetation relationships. Warmth index (WI) and drought index (ER, evaporation rate) were used to represent the site conditions. Life zones, represented by potential vegetation, were derived based on the combinations of WI and ER. With constant evaporation, the shift of life zone under increased temperature (+2 and+4^°C) and decreased precipitation (-20 and -40mm) was predicted. The results show that the life zones are sensitive to environmental perturbation, e. g. the southern edge of broadleaved conifer mixed forest zone would go up 100-300 km if temperature increases 2^°C, and the boundary between steppe and forest would shift 100-200 km towards the east if annual precipitation decreases 20 mm. This study is considered meaningful for ecosystem management when making strategy to the changing climate, especially for rescuing the distinct species.

View full abstract

Indonesian forest fire took place in a wide area of Kalimantan and Sumatera Islands in 1997 and continuously influenced the atmospheric environment and meteorological conditions of South-East Asia nearly throughout the last half of the year. The fire produced various materials including chemical species and particles, which drastically changed the aerosol optical properties in the area. A retrieval algorithm developed for MODIS is applied to the NOAA AVHRR visible and near infrared channels. The method is based on a look-up table, pre-calculated with the 6S code. Five accumulation modes and six coarse modes are used to constitute an aerosol size distribution with two lognormal functions. Satellite data of NOAA 14 for the period of Oct. 8 and Oct. 9, 1997 are analyzed. We derive aerosol optical thickness and the fractional contribution of the accumulation mode to the total radiance, rt, over the ocean area between the two islands. A highly changeable feature is derived with regard to the aerosol properties in the time period. The results are validated with day-averaged surface meteorological data and sun-photometer data. A comparison is made with the results using the aerosol model of Amazon biomass burning.

View full abstract

A scaling technique was investigated to extrapolate the local information on land cover derived from high spatial resolution data (LANDSAT/TM) to more extensive area through low spatial resolution data (NOAA/AVHRR). The error of overlay between AVHRR data and TM data was evaluated to ensure the following analysis. Over a combined data set of TM and AVHRR, at first, land cover types were classified into three categories including vegetation, water, and dried non-vegetation with TM data, and next, AVHRR image density was statistically regressed with category mixture conditions derived from TM pixels in each AVHRR pixel. Based on the regression model, the land cover category mixing ratio was estimated from AVHRR data by extrapolate the model to the whole coverage of AVHRR data. As a result, we found that end-members of AVHRR data for each land cover category was under estimated. It is partially because that a large part of TM pixels are also mixture pixels. Taking this into account, we used the vegetation-soil-water index (VSWI) as a key to estimate the end-member of AVHRR data from related TM data. AVHRR VSW index is difficult to determine from AVHRR data only, because there are very few pure pixels for vegetation, soil or water to determine accurate end-members for each land cover category. In this study, we investigated a scaling method to estimate AVHRR VSW index by means of the regression analysis relating NOAA/AVHRR CCT counts in both of ch.1 and 2 with LANDSAT/TM VSW index.

View full abstract

A new prediction method for time series data with high missing data ratio is proposed. The method does not require the assumption that time series data is derived from a linear process. It is found that the prediction error of the proposed method is 8.4 to 90.0% smaller than that of the existing method of RLS (Recursive Least Square) method for DMSP (Defence Meteorological Satellite Program) /SSM/I (Special Sensor of Microwave/Imager) data.

View full abstract

The field campaign for the vicarious calibration of ASTER/VNIR and SWIR was conducted at Tsukuba test site on December 13 and 14 1997. A comparison of the measured surface reflectance of the grass field and asphalt at the test site, optical depth as well as Top of Atmosphere (ToA) radiance was made among four institutes, University of Arizona, Geophysical Survey of Japan, Kanazawa Institute of Technology and Saga University. Approimately 8% of descrepancy on the mesured reflectance is found among the institutes while about 3% of the estimated optical depth and around 2% of the estimated ToA radiance are also found. Further improvement on the surface reflectance measurement, in particular, is highly required.

View full abstract

A preliminary field experiment for ASTER vicarious calibration (VC) was held in Tsukuba, Japan, on December 13 and 14 in 1997. Activities for ASTER/TIR (channels 10 to 14) in the experiment were water temperature measurements on Lake Kasumigaura at NOAA14 overpass times and four radiosonde observations per day. In the present paper, the effectivity of the VC of ASTER/TIR using the lake in winter is evaluated based on results from these activities.
First, the top-of-atmosphere brightness temperatures (TOA-BTs) for AVHRR channels 4 and 5 are calculated from the VC with the in-situ measurements, and show very good agreements (<0.3K) with the TOA-BTs from the onboard calibration. Then, the TOA-BTs for ASTER/TIR channels are calculated with radiosonde profiles and NCEP GDAS (global data assimilation system) profiles around the lake during the experimental period, and show very good agreements (<0.3 K) with each other ; because the atmosphere around the lake was stable during the period; and because the GDAS profiles around the lake have high accuracy owing to a nearby permanent weather station. Finally, the sensitivity of input parameters to the VC of ASTER/TIR is analyzed under conditions around the lake in winter. The results show that the measurement errors of water vapor and air temperature profiles by a radiosonde are small enough for VC, the ozone profile and visibility (aerosols) errors degrades the VC of channel 12 and transparent channels respectively, and the accuracy of VC is most sensitive to water skin temperature.
In the future, the VC of actual ASTER/TIR channels using the lake in winter will be executed based on the results from the present paper.

View full abstract