The region of Japan along the Japan Sea is one of the heaviest snowfall regions in the world, and it appears to be increasingly vulnerable to climate variability and global warming. This study ...investigated the long‐term trends in snowfall characteristics and extremes (i.e., heavy snowfall) over Japan mainly using station observations over 51 years from the 1961/1962 to 2011/2012 winter seasons. Long‐term trends were examined in terms of total precipitation and the ratio of the numbers of snowfall days to precipitation days R(s/p). Our results show statistically significant decreasing trends in seasonally accumulated snowfall at most stations in Japan, except for those in northern Tohoku and Hokkaido Districts and the Pacific side of Japan. These significant decreasing snowfall trends were associated with the long‐term decrease in R(s/p). Although long‐term decreasing trends in R(s/p) were also observed over Tohoku District and Pacific side, increasing trends in precipitation cancelled the decreasing trends there, which indicates long‐term trends in precipitation likely complicated snowfall trends. Over Hokuriku District, a decrease in precipitation enhanced the decrease in snowfall. Moreover, major snowfall events occurred in the first half of the study period, whereas a recent increase in heavy snowfall was not yet evident.
The region of Japan along the Japan Sea is one of the heaviest snowfall regions in the world, and it appears to be increasingly vulnerable to climate variability and global warming. Long‐term trends were examined in terms of total precipitation and the ratio of the numbers of snowfall days to precipitation days R(s/p). Although the decreasing trends in R(s/p) due to SAT warming can explain most decreasing trends in snowfall, increasing trends in precipitation cancelled the decreasing trends, which indicates long‐term trends in precipitation likely complicated snowfall trends. Over some regions, a decrease in precipitation enhanced the decrease in snowfall. Moreover, major snowfall events occurred in the first half of the study period, whereas a recent increase in heavy snowfall was not yet evident.
Abstract
East of Eurasia, moist air is transported poleward, forming the Meiyu–Baiu front over East Asia in late June and early July. Recently, unusually heavy rainfall may have increased, causing ...catastrophic flooding in East Asia. Here, unique 23-year precipitation satellite radar data confirm recent enhancement in Meiyu–Baiu heavy rainfall from eastern China to southwestern Japan, which is also evident from independent conventional observations. Decadal changes in rainfall have been physically consistent with enhanced transport of water vapour due to the intensified Pacific subtropical high associated with weakened tropical cyclone activity over the Northwest Pacific. Furthermore, the upper-tropospheric trough, associated with wave train along the subtropical jet, influenced Meiyu–Baiu precipitation over East Asia. Long-term and continuous satellite radar observations reveal that the frequency of heavy precipitation along the Meiyu–Baiu front has increased in the last 22 years. In particular, heavy precipitation (10 mm/h) increased by 24% between 1998–2008 and 2009–2019, and the abruptly-changed level likely induced recent meteorological disasters across East Asia. This trend may also explain the severity of the 2020 Meiyu–Baiu season. Over the last decade, this front has likely transitioned to a new climate state, which requires adaptation of disaster prevention approaches.
Dynamical downscaling with a 20 km horizontal resolution was undertaken over East Asia for the period May–August in 1991–2015 using the Weather Research and Forecasting (WRF) model with Grell-3D ...ensemble cumulus parameterization as a product of the Impact of Initialized Land Temperature and Snowpack on Sub-Seasonal to Seasonal Prediction (LS4P) program. Simulated climatological precipitation biases were investigated over land during June when heavy precipitation occurred. Simulations underestimated precipitation along the Meiyu/Baiu rainband, while overestimating it farther north. Dry and wet biases expanded to south and north of the Yangtze River in China, respectively, marking years with poor precipitation simulations. Model biases in synoptic-scale circulation patterns indicate a weakened clockwise circulation over the western North Pacific in the model due to active convection there, and suppressed northward moisture transport to the Meiyu/Baiu rainband. Moisture convergence was slightly enhanced over central China due to an apparent anticyclonic circulation bias over northern China. In years with large biases, positive feedback between reduced moisture inflow and inactive convection occurred over southern China, while moisture transport to central China intensified on regional scales, with amplification of dry and wet biases over China. The Kain–Fritch scheme was used to test the influence of cumulus parameterization, improving the dry bias over southern China due to the modification of synoptic-scale circulation patterns in the lower troposphere. However, precipitation was further overestimated over central China, with the accuracy of precipitation distribution deteriorating.
Long-term changes in the interannual variation in summer seasonal June–August (JJA) precipitation over the tropical Asian summer monsoon (ASM) region were investigated using 22 simulations from phase ...5 of the Coupled Model Intercomparison Project (CMIP5) of the representative concentration pathway 4.5 (RCP4.5) run. Objective evaluations were performed with statistical tests to determine if there was an agreement among the multiple models. A robust increasing trend in fluctuations in the interannual variation in JJA precipitation over the ASM region was found. Expansions in both the wet and dry extremes of JJA precipitation anomalies were identified from the beginning to end of the twenty-first century, which were indicative of an intensification in interannual variation. These results indicate that the frequency and/or intensity of floods and droughts will likely increase under global warming. The spatial distribution of the projected expansion of wet and dry extremes differed over the ASM region. The signals in the wet extreme appeared throughout the whole ASM region, whereas those in the dry extreme were strong, particularly over the area from the Bay of Bengal to the equatorial western North Pacific, corresponding with the monsoon trough where the mean JJA precipitation increased.
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BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Existing research on the role of gonadotropin-releasing hormone (GnRH) in bivalve reproduction is inadequate, even though a few bivalve GnRH orthologs have been cloned. The objective of this paper ...was to elucidate the in vivo effect of GnRH administration in Yesso scallop reproduction. We performed in vivo administration of scallop GnRH (py-GnRH) synthetic peptide into the developing gonad, and analyzed its effect on gonad development for 6 weeks during the reproductive season. The resulting sex ratio in the GnRH administered (GnRH(+)) group might be male biased, whereas the control (GnRH(-)) group had an equal sex ratio throughout the experiment. The gonad index (GI) of males in the GnRH(+) group increased from week 2 to 24.8% at week 6. By contrast the GI of the GnRH(-) group peaked in week 4 at 16.6%. No significant difference was seen in female GI between the GnRH(+) and GnRH(-) groups at any sampling point. Oocyte diameter in the GnRH(+) group remained constant (about 42-45 μm) throughout the experiment, while in the GnRH(-) group it increased from 45 to 68 μm i.e. normal oocyte growth. The number of spermatogonia in the germinal acini of males in the GnRH(+) group increased from week 4 to 6. Hermaphrodites appeared in the GnRH(+) group in weeks 2 and 4. Their gonads contained many apoptotic cells including oocytes. In conclusion, this study suggests that py-GnRH administration could have a potential to accelerate spermatogenesis and cause an inhibitory effect on oocyte growth in scallops.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The present study examined extreme rainfall events (EREs) in central India during the summer monsoon season, focusing on their spatial characteristics. A station‐based gridded and a ...station‐satellite‐blended dataset was used to examine long‐term and recent variations in precipitation characteristics for 50 years (1951–2000) and 38 years (1981–2018), respectively. A precipitation system approach (PSA) was applied to identify the ERE precipitation systems and categorized spatial sizes of ERE systems into three categories: sporadic, intermediate, and massive ERE precipitation systems. Conventionally, the ERE frequency is equal to the total number of ERE grids, whereas PSA counts ERE systems. The sporadic precipitation grid contributes 42% of all the ERE grids, and sporadic EREs frequency increases in the long‐term. The long‐term trend of intermediate and massive EREs does not increase and quite sharply increases, respectively, and these EREs are also intensifying. Recent 38 years have shown a reverse in the trends of ERE characteristics, the frequency and intensity of intermediate and massive EREs have decreased, whereas the massive ERE systems are broadening.
In general, different sizes of precipitation systems associated with phenomena such as thunderstorms, meso‐scale systems or synoptic systems occur in the environment. A large difference in the long‐term analysis of extreme rainfall events over central India can be seen between the grid based conventional approach and the precipitation system approach. Precipitation system approach gives more physical meaning of the extreme rainfall events long‐term changes.
Precipitation sensitivity to soil moisture and its seasonal and diurnal changes are investigated in Bangladesh and surrounding regions using a regional climate model with a 5-km grid spacing. In the ...control experiment, soil moisture is calculated by a land surface scheme, and simulated accuracy of seasonal and diurnal variations in precipitation intensity and frequency is capable of assessing the soil moisture impact on precipitation. In sensitivity experiments with wetter land surfaces, daytime precipitation intensity decreases over the southern plains for both the premonsoon and mature monsoon seasons because of the weakening of surface heating and vertical mixing in the planetary boundary layer (PBL). Weakened vertical turbulent flux of moisture reduces condensation heating and upward motion in the mid- and upper troposphere, which suppresses development of convective precipitation. The simulated precipitation intensity response to soil moisture suggests that land surface wetness contributes to the seasonal contrast in observed precipitation intensity (i.e., stronger in the premonsoon than the mature monsoon seasons). Meanwhile, the precipitation frequency response to soil moisture varies with season and by region. Over the southern plains in the wet land surface experiments, daytime precipitation frequency decreases (increases) during the premonsoon (mature monsoon) season compared with the dry land surface experiments, as influenced by seasonal differences in relative humidity and the condensation process in the lower troposphere. Around the northern mountainous area, higher soil moisture increases precipitation frequency regardless of season because of additional water vapor supply from the ground and frequent orographic precipitation forced by the mountainous topography.
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Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The atmospheric circulation patterns that were responsible for the heavy flooding that occurred in Thailand in 2011 are examined. This paper also investigates the interannual variation in ...precipitation over Indochina over a 33-yr period from 1979–2011, focusing on the role of westward-propagating tropical cyclones (TCs) over the Asian monsoon region. Cyclonic anomalies and more westward-propagating TCs than expected from the climatology of the area were observed in 2011 along the monsoon trough from the northern Indian subcontinent, the Bay of Bengal, Indochina, and the western North Pacific, which contributed significantly to the 2011 Thai flood. The strength of monsoon westerlies was normal, which implies that the monsoon westerly was not responsible for the seasonal heavy rainfall in 2011. Similar results were also obtained from the 33-yr statistical analysis. The 5-month total precipitation over Indochina covaried interannually with that along the monsoon trough. In addition, above-normal precipitation over Indochina was observed when enhanced cyclonic circulation with more westward-propagating TCs along the monsoon trough was observed. Notably, the above-normal precipitation was not due to the enhanced monsoon westerly over Indochina. Therefore, the 2011 Thai flood was caused by the typical atmospheric circulation pattern for an above-normal precipitation year. It is noteworthy that the effect of sea surface temperature (SST) forcing over the western North Pacific and the Niño-3.4 region on total precipitation during the summer rainy season over Indochina was unclear over the 33-yr period.
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Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A numerical experiment with a 2-km resolution was conducted using the Weather Research and Forecasting (WRF) Model to investigate physical processes driving nocturnal precipitation over the Himalayas ...during the mature monsoon seasons between 2003 and 2010. The WRF Model simulations of increases in precipitation twice a day, one in the afternoon and another around midnight, over the Himalayan slopes, and of the single nocturnal peak over the Himalayan foothills were reasonably accurate. To understand the synoptic-scale moisture transport and its local-scale convergence generating the nocturnal precipitation, composite analyses were conducted using the reanalysis dataset and model outputs. In the synoptic scale, moisture transport associated with the westward propagation of low pressure systems was found when nocturnal precipitation dominated over the Himalayan slopes. In contrast, moisture was directly provided from the synoptic-scale monsoon westerlies for nocturnal precipitation over the foothills. The model outputs suggested that precipitation occurred on the mountain ridges in the Himalayas during the afternoon and expanded horizontally toward lower-elevation areas through the night. During the nighttime, the downslope wind was caused by radiative cooling at the surface and was intensified by evaporative cooling by hydrometeors in the near-surface layer. As a result, convergence between the downslope wind and the synoptic-scale flow promoted nocturnal precipitation over the Himalayas and to the south, as well as the moisture convergence by orography and/or synoptic-scale circulation patterns. The nocturnal precipitation over the Himalayas was not simulated well when we used the coarse topographic resolution and the smaller number of vertical layers.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This paper presents a comprehensive analysis of the effect of urbanization on the surface air temperature (SAT) from 1951 to 2018 in the Philippines. The daily minimum temperature (Tmin) and daily ...maximum temperature (Tmax) records from 34 meteorological stations were used to derive extreme temperature indices. These stations were then classified as urban or rural based on satellite night‐lights. The results showed a significant difference in the SAT trends between urban and rural stations, indicative of the effect of urbanization in the country. Larger and more significant warming trends were observed in indices related to Tmin than those related to Tmax. In particular, the effects of urbanization were significant in the annual index series of Tmin, diurnal temperature range, minimum Tmin, percentage of days when Tmin was less than the 10th percentile (TN10p), percentage of days when Tmin was greater than 90th percentile (TN90p), and the number of coldest nights. The effects of urbanization were not as clear on the index series of maximum Tmax (TXx), minimum Tmax (TXn), percentage of days when Tmax was less than 10th percentile (TX10p), and the number of hottest days. The effects of urbanization on the annual series of extreme temperature indices were statistically significant at the 95% confidence level, with the exception of Tmax, TXn, TXx, TX10p, and the number of hottest days. Further analysis revealed that the effect of urbanization was the greatest during the DJF (December–January–February) season. These findings serve as a baseline study that focuses on the countrywide effect of urbanization on SAT trends in the Philippines.
The 34 synoptic stations in the Philippines were classified into urban and rural stations based on the satellite nightlights to estimate the effect of urbanization on the trends of extreme temperature indices (e.g., (a) Tmin and (b) Tmax) in the country for the first time. The results show that larger and significant effects of urbanization were found in the annual indices related to Tmin as compared to those indices related to Tmax. Further analysis reveals that the maximum urbanization effect occurred during the winter season.
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