Difference Between Cloud Top Height and Storm Height 2 for Heavy Rainfall using TRMM Measurements

This study compares the regional characteristics of heavy rain clouds in terms of Cloud Top Height (CTH) and Storm Height (SH) from long-term Tropical Rainfall 35 Measuring Mission (TRMM) observations. The SH is derived from Precipitation Radar 36 reflectivity and the CTH is estimated using Visible and InfraRed Scanner brightness 37 temperature (10.8 μm) and reanalysis temperature profiles. As the rain rate increases, 38 the average CTH and average SH increase, but by different degrees in different regions. 39 Heavy rainfall in continental rainfall regimes such as Central Africa and the United States 40 is characterized by high SH, in contrast to oceanic rainfall regions such as the 41 northwestern Pacific, Korea, and Japan; the increase of atmospheric instability in dry 42 environments is interpreted as a mechanism of continental floods. Conversely, heavy 43 rain events in Korea and Japan occur in a thermodynamically near-neutral environment 44 with large amounts of water vapor; these are characterized by the lowest CTH, SH, and 45 ice water content. The northwestern Pacific exhibits the lowest SH in humid 46 environments, similar to Korea and Japan; however, this region also characteristically 47 exhibits the highest convective instability condition as well as high CTH and CTH−SH 48 values, in contrast to Korea and Japan. The observed CTH and SH characteristics of 49 heavy rain clouds are expected to be useful for the evaluation and improvement of 50 satellite-based precipitation estimation and numerical model cloud parameterization.

States, and argued that warm-type heavy rain (in contrast to cold-type) dominates the 84 precipitation system of Korean peninsula. Subsequently, Song and Sohn (2015) reported 85 that warm-type heavy rain classified from PR reflectivity profiles is not limited to the Korean 86 peninsula, but a common precipitation structure shown in the NW Pacific and East Asia 87 monsoon environments. This feature has led to significant problems for satellite-based  differences with the conclusion of Song and Sohn (2015), who stated that the vertical 114 structures of heavy rain around the NW Pacific Ocean and the Korean peninsula display a 115 similar structure in radar reflectivity profiles. This implies that fundamental differences 116 exists between the CTH obtained by TB11 and the SH derived from reflectivity profiles.

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Based on this concept, many previous studies have analyzed the joint probability density . The TB11 and SH characteristics of these four regions are interesting because it is 129 expected that SH is sensitive to the continental and oceanic precipitation system, and TB11 130 differs between tropical and middle latitude regions. Because it is expected that regional 131 characteristics will be more distinct for heavy rain clouds than light rain clouds, this study 132 focuses on the characteristics of heavy rain clouds. Instead of using the TB11 data, this 133 6 study investigates the difference between CTH and SH in terms of the altitude scale by 134 converting TB11 data into CTH format along with reanalysis data. Furthermore, this study 135 discusses the mechanism behind regional differences in CTH and SH.    This study attempted to calculate the CTH of precipitation clouds from VIRS TB11 data 178 by referring to the temperature profiles of ERA-Interim data. In the case of opaque clouds 179 such as precipitation clouds, TB11 can be used to approximate cloud top temperature.

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The regional differences between heavy rain clouds revealed in previous studies can be 207 related to problems of satellite precipitation estimation. For example, Sekaranom and 208 Masunaga (2019) showed that the regional difference of PR and TMI rain products 209 (focusing on oceanic and continental convection), resulting from characteristics that PR 210 tends to detect more organized heavy rain system under the humid environment, whereas 211 the TMI rainfall is sensitive to deep convective clouds under relatively dry and unstable 212 condition. Figure 1a shows the average value of TMPA summer precipitation. In general, rain rate intensity increases (e.g., 10 > mm h -1 , 40 > mm h -1 ). The SH of extreme heavy rain 274 shown in Fig. 3f is more than 9 km in continental precipitation regions (e.g., Central Africa, 275 China, the United States), and less than 9 km in oceanic precipitation regions (e.g., ocean precipitation regions (Fig. 1a). The CTH of extreme heavy rain clouds shows different 283 characteristics to the SH of those (Fig. 3e). In continental precipitation regions, maximum

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CTH is approximately 15 km, which is higher than SH because the SH is already high. The 285 average CTH is high (13-14 km) in the ITCZ, similar to the average precipitation (Fig. 1a) Figure 4a shows the spatial distribution of the difference between CTH and SH for  in CTH and SH between these regions can be explained by the difference in the 320 thermodynamic environment. In fact, the CAPE is typically high in tropical regions (Fig. 4b) 321 and the TPW exhibits maximum values in South Asia, NW Pacific, and East Asia monsoon 322 regions (Fig. 4c). Specifically, because ConQ is high around Korea/Japan, the dynamic 323 conditions for producing heavy rainfall are satisfied over those regions (Fig. 4d). When the 324 average values are examined for the four regions (Table 1) the mean CTH−SH of extreme heavy rain clouds in the Eastern Pacific is still higher than 333 that in the Korea/Japan because of relatively high CTH in the EP (Fig. 3e). Therefore, the 334 small difference between CTH and SH of extreme heavy rain clouds found in Korea and 335 Japan seems to be very unique.

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For a more detailed analysis, Fig. 5 shows the PDF distributions for CTH and SH, as well 337 as the thermodynamic environment variables of extreme heavy rain. First, in the CTH 338 distribution (Fig. 5a), double peaks appear in every region. Among them, the peak located 339 at the lower height corresponds to a location below the tropopause height during the 340 process of allocating the VIRS TB11 to the vertical distribution of ERA-Interim temperatures.

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The peak located at a higher altitude corresponds to the case in which the peak is outside 342 of the ERA-Interim data; thus, the climatology of AIRS/AMSU tropopause height is 343 substituted. Note that different treatment of tropopause height will not much change the the results between NW Pacific and Korea/Japan are very similar (Fig. 5b), which is 352 consistent with the results from Song and Sohn (2015). Compared to these regions, the 353 United States and Central Africa exhibit many cases where SH is greater than or equal to 354 10 km. In particular, in the United States, the SH is often in the 10-15 km range, and in 355 Central Africa, the SH is often greater than or equal to 15 km. The average SH is similar 356 between these two regions (Table 1).

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The resulting CTH−SH distribution is the largest in the NW Pacific, followed by 358 Korea/Japan, Central Africa, and the United States (Fig. 5c). For example, the proportion of 359 CTH−SH cases with a thickness of greater than or equal to 4 km in the NW Pacific,

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Korea/Japan, Central Africa, and the United States is 74%, 59%, 51%, and 24%, 361 respectively. The proportion of CAPE cases of greater than or equal to 1,000 K kg -1 , which 362 can provide the thermodynamic energy for the growth of deep convective clouds in the NW

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Pacific, Central Africa, the United States, and Korea/Japan is 75%, 52%, 34%, and 17%, 364 respectively (Fig. 5d). It is determined that the order of CAPE values is closely related to  (Table 1). Cases where ConQ is higher than 0.5 g m -2 s -1 appear 372 most frequently in Korea/Japan among the four regions (Fig. 5f), indicating dynamically 373 18 favorable conditions for heavy rainfall.
374 Figure 6 shows the joint frequency distribution of IWC observed from the CloudSat CPR.

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The occurrence of heavy rain cannot be determined using CPR observations alone.

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However, the IWC distribution above the SH for heavy rain clouds can be inferred from the 377 fact that the SH of heavy rain is typically higher than 9 km. The proportion of cases where 378 the IWC is greater than 2 g m -3 (above approximately 9 km) is 0.38%, 0.26%, 0.12%, and 379 0.03% in the United States, Central Africa, the NW Pacific, and Korea/Japan, respectively, 380 in descending order. The fact that the average rain rate is higher and the PCT85 is lower 381 (i.e., indicating abundant IWC) in the United States than in Central Africa for extreme heavy 382 rain clouds (Table 1) partially explains the proportion of high IWC in the United States.

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However, considering that the occurrence of extreme heavy rain clouds between two 384 regions is similar despite of the relatively frequent visit number of TRMM satellite for 385 mid-latitudes more than twice as much as that for tropics, the relative occurrence frequency 386 of heavy rain clouds in the United States is less than half of that in Central Africa, implying 387 more suppressed convection over the United States. Rather, it can be interpreted that 388 clouds accompanied by abundant IWC produce localized heavy rain cases in the United

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States. The small proportion of high IWC in the NW Pacific and Korea/Japan is consistent 390 with a relatively high PCT85 (Table 1). Because the NW Pacific has a deeper cloud layer confirming that CPR reflectivity was observed for the layer between the SH and the CTH.

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However, it was determined that the match-up data of TRMM and CloudSat satellites was 439 highly insufficient for studying the regional characteristics of precipitating clouds.