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Motuo and Naqu are two typical regions of the Tibetan Plateau with different geographical locations and climate regimes. These differences may lead to discrepancies in the raindrop size distributions (DSDs) and precipitation microphysical processes between the two regions. This paper investigates discrepancies in the DSDs using disdrometer data obtained during the rainy season in Motuo and Naqu. The DSD characteristics are studied under five different rainfall rate categories and two precipitation types (stratiform and convective). For the total data sets, the number concentrations of drops with diameters D > 0.6 (D < 0.6) mm are higher (lower) in Naqu than in Motuo. The fitted normalized gamma distributions of the averaged DSDs for the five rainfall rate categories show that Naqu has a larger (lower) mass-weighted mean diameter Dm (normalized intercept parameter, log10Nw) than does Motuo. The difference in Dm between Naqu and Motuo increases with the rainfall rate. Convective clusters in Naqu could be identified as continental-like, while convective precipitation in Motuo could be classified as maritime-like. The relationships between the shape factor μ and slope parameter Λ of the gamma distribution model, the radar reflectivity Z and the rainfall rate R are also derived. Furthermore, the possible causative mechanism for the notable DSD variation between the two regions during the rainy season is illustrated using reanalysis data and automated weather station observations. Cold rain processes are mainly responsible for the low concentrations of large drops observed in Naqu, whereas warm rain prevails in Motuo, producing abundant small drops.

The NWCSAF (Support to Nowcasting and Very Short Range Forecasting Satellite Application Facility) software package provides operational products that ensure the optimum use of meteorological satellite data in Nowcasting and Very Short Range Forecasting. The National Observatory of Athens operates NWCSAF since 2016. The rainfall estimates obtained by the Convective Rainfall Rate (CRR) nighttime algorithm and the Convective Rainfall Rate from Cloud Physical Properties (CRR-Ph) algorithm of the 2016 version are verified against rainfall observations provided by the dense network of automated surface weather stations operated by the National Observatory of Athens (NOA) for a full year. For the verification a temporal upscaling to 30 min was applied to all datasets. Overall, CRR overestimates the extent of the precipitation areas while at the same time it underestimates the precipitation totals. CRR-Ph clearly outperforms the CRR nighttime algorithm regarding the accurate delineation of precipitation areas but it overestimates the precipitation totals. Heavier precipitation is consistently detected by both algorithms although the false alarms rate is high. Seasonal variations are found, with the most important the poorer estimation performance during spring.

The characteristics of raindrop size distribution (DSD) over the Tibetan Plateau and southern China are studied in this paper, using the DSD data from April to August 2014 collected by HSC-PS32 disdrometers in Nagqu and Yangjiang, comprising a total of 9430 and 6366 1-min raindrop spectra, respectively. The raindrop spectra, characteristics of parameter variations with rainfall rate, and the relationships between reflectivity factor (Z) and rainfall rate (R) are analyzed, as well as their DSD changes with precipitation type and rainfall rate. The results show that the average raindrop spectra appear to be one-peak curves, the number concentration for larger drops increase significantly with rainfall rate, and its value over southern China is much higher, especially in convective rain. Standardized Gamma distributions better describe DSD for larger drops, especially for convective rain in southern China. All three Gamma parameters for stratiform precipitation over the Tibetan Plateau are much higher, while its shape parameter (μ) and mass-weighted mean diameter (D m), for convective precipitation, are less. In terms of parameter variation with rainfall rate, the normalized intercept parameter (N w) over the Tibetan Plateau for stratiform rain increases with rainfall rate, which is opposite to the situation in convective rain. The μ over the Tibetan Plateau for stratiform and convective precipitation types decreases with an increase in rainfall rate, which is opposite to the case for D m variation. In Z–R relationships, like “Z = AR b ”, the coefficient A over the Tibetan Plateau is smaller, while its b is higher, when the rain type transfers from stratiform to convective ones. Furthermore, with an increase in rainfall rate, parameters A and b over southern China increase gradually, while A over the Tibetan Plateau decreases substantially, which differs from the findings of previous studies. In terms of geographic location and climate over the Tibetan Plateau and southern China, the precipitation in the pre-flood seasons is dominated by strong convective rain, while weak convective rain occurs frequently in northern Tibet with lower humidity and higher altitude.

The effect of rain on the microwave systems is more critical especially for countries located in tropical and equatorial region that experience high rainfall rate throughout the year. In order to predict a reliable and an accurate rain prediction model, it is required to determine the one-minute integration time of rainfall rate together with direct measurement of rain attenuation. In order to counter the current trend of employing higher frequencies especially in tropical and equatorial regions, there is an urgent need to carry out studies related to the effect of rain in order to get a better rain attenuation prediction model. Therefore, the purpose of this study is to investigate the effect of rain on terrestrial microwave system operating at 26 GHz in Malaysia. The rain intensity with one minute integration time is measured at Universiti Teknologi Malaysia-Skudai (UTM-Skudai) and 99 rain gauges located throughout the Peninsular Malaysia. This study explains the detailed experimental set up and analyses of both rain rate and rain attenuation measurements. The analysis on large-scale study area includes the comparisons between the measured rainfall data and the Drainage and Irrigation Department (DID) rainfall data and also with the Malaysia Meteorological Services (MMS) rainfall data. This study has successfully proposed a new rain rate and rain attenuation prediction model and the obtained results show satisfactory performance and good agreement.

Chernobyl radioactivity in precipitation was measured at Tsukuba, Japan, as were both surface-air concentrations and particle-size distributions of Chernobyl-released radionuclides. To understand the wet removal processes of the Chernobyl radionuclides, i.e.137Cs,103Ru, and90Sr, wet deposition velocities were calculated. The wet deposition velocities of the Chernobyl radioactivity for individual rainfall events varied largely. The wet deposition velocity is given as the product of washout ratio and rainfall rate. Typically, it was found that the washout ratios of90Sr are systematically larger than those of137Cs. In order to explain this fact, we examined the relationship between the washout ratios and particle sizes of radionuclide-bearing aerosols. A positive correlation between corrected washout ratios and particle size was found with a particle diameter range from 0.35 to 1.2 µm. The result strongly suggests that the factors controlling the wet removal of the Chernobyl radioactivity for individual rainfall events are surface air concentration, particle size, and rainfall rate, rather than precipitation amount, which is in agreement with previous understandings. This suggests that high contamination areas of radioactivity are formed during heavy rainfall events with high rainfall rates in the case of tropospheric injection such as the Chernobyl accident.

Current-climate precipitation and temperature extremes have been identified by decision makers in West Africa as among the more impactful weather events causing lasting socioeconomic damage. In this article, we use a plausible future-climate scenario (RCP8.5) for the end of the twenty-first century to explore the relative commonness of such extremes under global warming. The analysis presented considers what a typical day in the future climate will feel like relative to current extrema. Across much of West Africa, we see that the typical future-climate day has maximum and minimum temperatures greater than 99.5% of currently experienced values. This finding exists for most months but is particularly pronounced during the Boreal spring and summer. The typical future precipitation event has a daily rainfall rate greater than 95% of current storms. These findings exist in both a future scenario model run with and without parameterised convection, and for many of the Coupled Model Inter-comparison Project version 5 ensemble members. Additionally, agronomic monsoon onset is projected to occur later and have greater inter-annual variability in the future. Our findings suggest far more extreme conditions in future climate over West Africa. The projected changes in temperature and precipitation could have serious socioeconomic implications, stressing the need for effective mitigation given the potential lack of adaptation pathways available to decision makers.

Based on the tropical rainfall measuring mission (TRMM)-measured rainfall and estimated outgoing longwave radiation (OLR) fields, it is found that 2007–08 Madden–Julian Oscillation (MJO07-08) went through blocking, splitting, and merging stages when it passed over the New Guinea Highlands (NGH). The TRMM-estimated OLR fields fail to capture detailed TRMM rainfall field and thus is not suitable to serve as proxy for rainfall, as also found in previous studies. The mechanism of orographic blocking is explained by strong orographic blocking on the incoming, low-Froude number, and moist flow, which belonged to the flow-around regime. This is evidenced by estimating the Froude number by upstream soundings. The strong blocking forced the flow to go around the mountains on NGH, leading to the splitting of flow and MJO precipitating system and the merging at the southeast tip of New Guinea. Orographic, MJO, and cyclone clouds were shown in both observed and model-simulated results. The major differences of the model-simulated and TRMM-measured precipitation are as follows: (a) the model-simulated rainfall area is much larger than that covered by the observed rainfall and (b) even though they both show comparable maximum rainfall rate, the rainfall estimated by TRMM reveals more localized rainfall spots, which is unexpected since the WRF simulation uses a relatively fine resolution (5 km). In summary, during the blocking stage, the mountains have slowed down the MJO propagation and increased the rainfall amount upstream of the local mountains, while during the splitting and merging stages, the mountains have made significant impacts on the MJO rainfall distribution.

Cloud is essential in the atmosphere, condensing water vapor and generating strong convective or large-scale persistent precipitation. In this work, the relationships between cloud vertical macro- or microphysical properties, radiative heating rate, and precipitation for convective and stratiform clouds in boreal summer over the Tibetan Plateau (TP) are analyzed and compared with its neighboring land and tropical oceans based on CloudSat/CALIPSO satellite measurements and TRMM precipitation data. The precipitation intensity caused by convective clouds is twofold stronger than that by stratiform clouds. The vertical macrophysics of both cloud types show similar features over the TP, with the region weakening the precipitation intensity and compressing the cloud vertical expansion and variation in cloud top height, but having an uplift effect on the average cloud top height. The vertical microphysics of both cloud types under conditions of no rain over the TP are characterized by lower-level ice water, ice particles with a relatively larger range of sizes, and a relatively lower occurrence of denser ice particles. The features are similar to other regions when precipitation enhances, but convective clouds gather denser and larger ice particles than stratiform clouds over the TP. The atmospheric shortwave (longwave) heating (cooling) rate strengthens with increased precipitation for both cloud types. The longwave cooling layer is thicker when the rainfall rate is less than 100 mm d−1, but the net heating layer is typically compressed for the profiles of both cloud types over the TP. This study provides insights into the associations between clouds and precipitation, and an observational basis for improving the simulation of convective and stratiform clouds over the TP in climate models.

West Africa is characterised by diverse hydro-climatic divisions ranging from the humid equatorial climate to the semi-arid and arid climates that manifest in high space–time variability in rainfall. In this study, drought and floods in six delineated domains (Northern Sahel, Southern Sahel, Sudanian, Western Guinea Coast, Central Guinea Coast and Eastern Guinea Coast) of West Africa were illustrated using the Standardized Precipitation Index (SPI 3 months and 9 months) calculated from global CPC Merged Analysis of precipitation (CMAP 2.5° by 2.5° resolution) data from 1980 to 2017. The trend analysis shows that none of the domains exhibits a significant trend in the computed SPI. However, there is a significant trend in the annual rainfall rate for all the domains except the Eastern Guinea Coast. Again, there is a likelihood of an increasing trend of SPI-3 but a decreasing trend for the SPI-9. The drier areas have significant increasing rainfall trend while the highly humid regions show significant negative trend except for the Eastern Guinea Coast that shows a non-significant very weak positive trend. The most exposed area to extreme drought conditions occurs over the northern Sahel domain at SPI-3 though the frequency of occurrence is very low. The Western Guinea coast experiences the highest number of dry events of about 32% of the time followed by the Northern Sahel domain. Under SPI-9, the following domains: Eastern Guinea coast, Sudanian, Northern Sahel and Western Guinea coast are prone to flooding incidence as they had 40%, 37%, 29% and 26% of wet events, respectively. The study recommends apt and timely climate service delivery, adoption of ecosystem-based adaptation strategies that promote apt and sustainable water management practices in the region.

To date, the intraseasonal variation of raindrop size distribution (DSD) in response to the Madden–Julian Oscillation (MJO) has been examined only over the Indonesian Maritime Continent, particularly in Sumatra. This paper presents the intraseasonal variation of DSD over the Indian Ocean during the Cooperative Indian Ocean experiment on Intraseasonal Variability in the Year 2011 (CINDY 2011) field campaign. The DSDs determined using a Joss–Waldvogel disdrometer, which was installed on the roof of the anti-rolling system of the R/V Mirai during stationary observation (25 September to 30 November 2011) at (8°S, 80.5°E), were analyzed. The vertical structure of precipitation was revealed by Tropical Rainfall Measuring Mission Precipitation Radar (version 7) data. While the general features of vertical structures of precipitation observed during the CINDY and Sumatra observation are similar, the intraseasonal variation of the DSD in response to the MJO at each location is slightly different. The DSDs during the active phase of the MJO are slightly broader than those during the inactive phase, which is indicated by a larger mass-weighted mean diameter value. Furthermore, the radar reflectivity during the active MJO phase is greater than that during the inactive phase at the same rainfall rate. The microphysical processes that generate large-sized drops over the ocean appear to be more dominant during the active MJO phase, in contrast to the observations made on land (Sumatra). This finding is consistent with the characteristics of radar reflectivity below the freezing level, storm height, bright band height, cloud effective radius, and aerosol optical depth.

In the present study, we have used TRMM multi-satellite precipitation analysis (TMPA) 3B42 and global precipitation mission (GPM): IMERG “precipitation Cal” products to identify and quantify the asymmetry and distribution of rainfall in tropical cyclones formed over Bay of Bengal (BoB). For the period 2010–2013, TMPA products have been made use of and for the period 2014–2017, GPM–IMERG products are used to study the aforementioned features. Overall, 17 cyclones covering 75 events/days ranging from depression to very severe cyclonic stage of the system have been analysed. Our analysis revealed some interesting features on asymmetry, direction of maximum rain-receiving zones, relation of T-number with maximum and total rainfall in rain-receiving areas. The study reveals the direction of rainfall zone is mostly towards west and southwest directions of the storm centre in BoB. This point gains importance in the context of earlier reports, where it is mentioned that the direction of maximum rainfall is in east. The study also infers that the maximum rainfall and total rainfall need not be dependent on the intensity (indicated by T-number). We also attempted to classify the rain-receiving zones, based on both the rainfall-rate window and area covered in each window of rainfall, and a criterion has been proposed. The distribution of rainfall is classified, as sharply falling, slowly falling and nearly constant.

It is recognized that rain attenuation is the primary factor in the degradation of Earth-satellite communication at the Ka band frequency. The beacon signal of the ROCSAT-1 is set at 19.5 GHz for downlink and 28.5 GHz for uplink. ROCSAT-1 is the low earth orbit (LEO) satellite with a circular orbit at the altitude of 600 km and 35° inclination angle and scheduled to be launched at the beginning of 1999. Given the extremely high frequency of the beacon, impairment of ROCSAT-1 communications due to rain attenuation should be seriously considered. In this paper, the ground-based instruments for the Ka band propagation experiments of ROCSAT-1, including Chung-Li VHF radar, 19.5 GHz radiometer, optical rain gauge, automatic weather station, and disdrometer, are introduced. The spatial distribution of the long-term statistics of rainfall rate is analyzed in this paper on the basis of 8 years (1988-1995) rainfall rate data at one-minute time resolution, recorded by more than 70 tipping bucket rain gauges distributed over Taiwan island. It shows a pronounced latitudinal variation in the percentage of time that the rainfall rate exceeds a specified level, indicating that more severe rain attenuation will be encountered in the southern part than that in the northern part of Taiwan. In addition, the sky noise temperature at the frequency of 19.5 GHz is measured by using a radiometer, both in the conditions of clear-air and precipitation. The observed sky noise temperature in the case of clear-air at the elevation angles of 90°, 60°, 30°, and 15° are respectively 50K, 80K, 100K, and 130K, corresponding to the attenuations of 0.7dB, 0.78dB, 1.2dB, and 2.7dB. Data analysis indicates that the observed clear-air sky noise temperature increasing exponentially with the decrease of the zenith angle is in perfect agreement with our theoretical prediction. The sky noise temperature in the case of precipitation is also investigated. A comparison between observed precipitation sky noise temperature and surface rainfall rate shows that a salient time shift in the two is seen, implying that great caution should be taken in establishing an empirical relationship between precipitation sky noise temperature and surface rainfall rate.

The characteristics and dynamics associated with the distribution, intensity, and triggering factors of local severe precipitation in Zhejiang Province induced by Super Typhoon Soudelor (2015) were investigated using mesoscale surface observations, radar reflectivity, satellite nephograms, and the final (FNL) analyses of the Global Forecasting System (GFS) of the National Center for Environmental Prediction (NCEP). The rainfall processes during Soudelor’s landfall and translation over East China could be separated into four stages based on rainfall characteristics such as distribution, intensity, and corresponding dynamics. The relatively less precipitation in the first stage resulted from interaction between the easterly wind to the north flank of this tropical cyclone (TC) and the coastal topography along the southeast of Zhejiang Province, China. With landfall of the TC in East China during the second stage, precipitation maxima occurred because of interaction between the TC’s principal rainbands and the local topography from northeastern Fujian Province to southwestern Zhejiang Province. The distribution of precipitation presented significant asymmetric features in the third stage with maximal rainfall bands in the northeast quadrant of the TC when Soudelor’s track turned from westward to northward as the TC decayed rapidly. Finally, during the northward to northeastward translation of the TC in the fourth stage, the interaction between a mid-latitude weather system and the northern part of the TC resulted in transfer of the maximum rainfall from the north of Zhejiang Province to the north of Jiangsu Province, which represented the end of rainfall in Zhejiang Province. Further quantitative calculations of the rainfall rate induced by the interaction between local topography and TC circulation (defined as “orographic effects”) in the context of a one-dimensional simplified model showed that orographic effects were the primary factor determining the intensity of precipitation in this case, and accounted for over 50% of the total precipitation. The asymmetric distribution of the TC’s rainbands was closely related to the asymmetric distribution of moisture resulted from changes of the TC’s structure, and led to asymmetric distribution of local intense precipitation induced by Soudelor. Based on analysis of this TC, it could be concluded that local severe rainfall in the coastal regions of East China is closely related to changes of TC structure and intensity, as well as the outer rainbands. In addition, precipitation intensity and duration will increase correspondingly because of the complex interactions between the TC and local topography, and the particular TC track along large-scale steering flow. The results of this study may be useful for the understanding, prediction, and warning of disasters induced by local extreme rainfall caused by TCs, especially for facilitating forecasting and warning of flooding and mudslides associated with torrential rain caused by interactions between landfalling TCs and coastal topography.

A series of charts of rainfall rates recorded by means of a Jardi pluviograph in Barcelona, Spain, and covering a period of 20 years have been digitised. The time intervals of exceedance of certain pre-set rainfall rate thresholds were computed and expressed in percentages of the whole 20-year period. The average worst month period and the absolute worst month were defined and computed. Results are found to agree well with those obtained elsewhere in Southern Europe; they are also compared with some published results for Kew. Frequency-distribution of rates as well as time of occurrence are presented. Rainfall amounts pertaining to several rainfall rate categories have been analysed in order to obtain the ratio of convective to total rainfall amount. Comparison of this ratio with results of some other authors is inconclusive.

A large sample of radar data from the period May–August 1976 was analyzed to provide information on the total areal coverage of precipitation echoes at 1-km steps in altitude ranging from 2 km up to 10 km. A transformation based on known statistics of surface rainfall rate was employed to express this information in terms of the probability of certain reflectivities being exceeded at a randomly chosen point at a given altitude. The same data base was used to construct a family of average vertical profiles of precipitation reflectivity. The profiles were conditioned by the reflectivity value at the lowest level (2 km), thus providing a basis for estimating the reflectivity aloft, given the low level or surface rainfall rate. Analyses of this kind have been reported for other geographical locations and for a variety of applications, such as hydrology, rain effects on earth-space radio propagation, and precipitation modeling. Similarities in the results from these two quite different analysis procedures, possibly not hitherto recognized, were found in the present study.

The characteristics of the raindrop size distribution for one hour during the passage of a West African thundersquall system over Ile-Ife (geog. lat. 7.5° N, long. 4.5° E) have been compared with those of a monsoon rainfall with comparably high rainfall rate. The significant difference observed between the drop size distributions at the beginning of the storm and those found later in the storm for equal rainfall rates has been attributed to the difference in the terminal velocities of the small and large drops and also the differences in the updraft velocities in the various parts of the storm. Such variations in drop size distribution were not observed for the monsoon rainfall. The intercept, No and the rainfall rate, R for the thunderstorm were found to be well correlated. No correlation was observed between the slope, ∧ and R. The reverse was the case for the monsoon rainfall. The empirical relationships obtained between the radar reflectivity factor, Z and the rainfall rate as well as between the liquid water content, M and the rainfall rate have been compared with the Marshall and Palmer results.

Measured differential phase shift ФDP is known to be a noisy unstable polarimetric radar variable, such that the quality of ФDP data has direct impact on specific differential phase shift KDP estimation, and subsequently, the KDP-based rainfall estimation. Over the past decades, many ФDP de-noising methods have been developed; however, the de-noising effects in these methods and their impact on KDP-based rainfall estimation lack comprehensive comparative analysis. In this study, simulated noisy ФDP data were generated and de-noised by using several methods such as finite-impulse response (FIR), Kalman, wavelet, traditional mean, and median filters. The biases were compared between KDP from simulated and observed ФDP radial profiles after de-noising by these methods. The results suggest that the complicated FIR, Kalman, and wavelet methods have a better de-noising effect than the traditional methods. After ФDP was de-noised, the accuracy of the KDP-based rainfall estimation increased significantly based on the analysis of three actual rainfall events. The improvement in estimation was more obvious when KDP was estimated with ФDP de-noised by Kalman, FIR, and wavelet methods when the average rainfall was heavier than 5 mm h ≥1. However, the improved estimation was not significant when the precipitation intensity further increased to a rainfall rate beyond 10 mm h ≥1. The performance of wavelet analysis was found to be the most stable of these filters.

Compared with daily rainfall amount, hourly rainfall rate represents rainfall intensity and the rainfall process more accurately, and thus is more suitable for studies of extreme rainfall events. The distribution functions of annual maximum hourly rainfall amount at 321 stations in China are quantified by the Generalized Extreme Value (GEV) distribution, and the threshold values of hourly rainfall intensity for 5-yr return period are estimated. The spatial distributions of the threshold exhibit significant regional differences, with low values in northwestern China and high values in northern China, the mid and lower reaches of the Yangtze River valley, the coastal areas of southern China, and the Sichuan basin. The duration and seasonality of the extreme precipitation with 5-yr return periods are further analyzed. The average duration of extreme precipitation events exceeds 12 h in the coastal regions, Yangtze River valley, and eastern slope of the Tibetan Plateau. The duration in northern China is relatively short. The extreme precipitation events develop more rapidly in mountain regions with large elevation differences than those in the plain areas. There are records of extreme precipitation in as early as April in southern China while extreme rainfall in northern China will not occur until late June. At most stations in China, the latest extreme precipitation happens in August-September. The extreme rainfall later than October can be found only at a small portion of stations in the coastal regions, the southern end of the Asian continent, and the southern part of southwestern China.

In this study, an effort has been made to study heavy rainfall events during cyclonic storms over Indian Ocean. This estimate is based on microwave observations from tropical rainfall measuring mission (TRMM) Microwave Imager (TMI). Regional scattering index (SI) developed for Indian region based on measurements at 19-, 21- and 85-GHz brightness temperature and polarization corrected temperature (PCT) at 85 GHz have been utilized in this study. These PCT and SI are collocated against Precipitation Radar (PR) onboard TRMM to establish a relationship between rainfall rate, PCT and SI. The retrieval technique using both linear and nonlinear regressions has been developed utilizing SI, PCT and the combination of SI and PCT. The results have been compared with the observations from PR. It was found that a nonlinear algorithm using combination of SI and PCT is more accurate than linear algorithm or nonlinear algorithm using either SI or PCT. Statistical comparison with PR exhibits the correlation coefficients (CC) of 0.68, 0.66 and 0.70, and root mean square error (RMSE) of 1.78, 1.96 and 1.68 mm/h from the observations of SI, PCT and combination of SI and PCT respectively using linear regressions. When nonlinear regression is used, the CC of 0.73, 0.71, 0.79 and RMSE of 1.64, 1.95, 1.54 mm/h are observed from the observations of SI, PCT and combination of SI and PCT, respectively. The error statistics for high rain events (above 10 mm/h) shows the CC of 0.58, 0.59, 0.60 and RMSE of 5.07, 5.47, 5.03 mm/h from the observations of SI, PCT and combination of SI and PCT, respectively, using linear regression, and on the other hand, use of nonlinear regression yields the CC of 0.66, 0.64, 0.71 and RMSE of 4.68, 5.78 and 4.02 mm/h from the observations of SI, PCT and combined SI and PCT, respectively.

This study investigates microphysical properties from wind profiler Doppler spectra observed within a precipitation system that produced high rainfall rates up to 40 mm hr−1 near the southern coast of the Korean Peninsula on 25∼26 June 2010. A 1290-MHz wind profiler located in the National Center for Intensive Observation of Severe Weather at Boseong, Korea, observed a widespread stratiform region and short-lived convective cells from 1850 UTC 25 to 0200 UTC 26 June 2010. By using a spectral model applied to observed profiler spectra, rainfall parameters and raindrop size distributions were retrieved below a melting layer during this period. Three representative periods during precipitation were selected based on intensities of bright band and characteristics in vertical profiles of radar reflectivity and Doppler velocity. During a brief convective period (∼30 min), radar reflectivity tended to be proportional to vertical air motion (positive upward), suggesting that updrafts up to ∼3 m s−1 over a large vertical extent through the melting layer probably contributed to increasing rainfall rates at the surface. In reflectivityrainfall rate distributions, large drop spectra (high reflectivity) were analyzed within downdrafts and small drop spectra (low reflectivity) within updrafts, similar to the large and small drop spectra but found in stratiform and convective regions, respectively, in previous studies. This indicates that the degree of spread between reflectivity and rainfall rate may be strongly dependent on positive and negative magnitudes of vertical air motion. For three categories of vertical air motion (i.e., updrafts, neutral, and downdrafts), physical relations between the retrieved rainfall parameters were examined.

The ability to forecast heavy rainfall associated with landfalling tropical cyclones (LTCs) can be improved with a better understanding of the mechanism of rainfall rates and distributions of LTCs. Research in the area of LTCs has shown that associated heavy rainfall is related closely to mechanisms such as moisture transport, extratropical transition (ET), interaction with monsoon surge, land surface processes or topographic effects, mesoscale convective system activities within the LTC, and boundary layer energy transfer etc.. LTCs interacting with environmental weather systems, especially the westerly trough and mei-yu front, could change the rainfall rate and distribution associated with these mid-latitude weather systems. Recently improved technologies have contributed to advancements within the areas of quantitative precipitation estimation (QPE) and quantitative precipitation forecasting (QPF). More specifically, progress has been due primarily to remote sensing observations and mesoscale numerical models which incorporate advanced assimilation techniques. Such progress may provide the tools necessary to improve rainfall forecasting techniques associated with LTCs in the future.

The accurate representation of rainfall in models of global climate has been a challenging task for climate modelers owing to its small space and time scales. Quantifying this variability is important for comparing simulations of atmospheric behavior with real time observations. In this regard, this paper compares both the statistical and dynamically forced aspects of precipitation variability simulated by the high-resolution (36 km) Nested Regional Climate Model (NRCM), with satellite observations from the Tropical Rainfall Measuring Mission (TRMM) 3B42 dataset and simulations from the Community Atmosphere Model (CAM) at T85 spatial resolution. Six years of rainfall rate data (2000–2005) from within the Tropics (30°S–30°N) have been used in the analysis and results are presented in terms of long-term mean rain rates, amplitude and phase of the annual cycle and seasonal mean maps of precipitation. Our primary focus is on characterizing the annual cycle of rainfall over four land regions of the Tropics namely, the Indian Monsoon, the Amazon, Tropical Africa and the North American monsoon. The lower tropospheric circulation patterns are analyzed in both the observations and the models to identify possible causes for biases in the simulated precipitation. The 6-year mean precipitation simulated by both models show substantial biases throughout the global Tropics with NRCM/CAM systematically underestimating/overestimating rainfall almost everywhere. The seasonal march of rainfall across the equator, following the motion of the sun, is clearly seen in the harmonic vector maps. The timing of peak rainfall (phase) produced by NRCM is in closer agreement with the observations compared to CAM. However like the long-time mean, the magnitude of seasonal mean rainfall is greatly underestimated by NRCM throughout the Tropical land mass. Some of these regional biases can be attributed to erroneous circulation and moisture surpluses/deficits in the lower troposphere in both models. Overall, the results seem to indicate that employing a higher spatial resolution (36 km) does not significantly improve simulation of precipitation. We speculate that a combination of several physics parameterizations and lack of model tuning gives rise to the observed differences between NRCM and the observations.

The effects of environmental vertical wind shear (VWS) on the intensity and rainfall asymmetries in Tropical Storm (TS) Bilis (2006) have been analyzed based on TRMM/TMI-estimated surface rainfall data, QuikSCAT wind fields, 850- and 200-hPa winds of the NCEP-NCAR reanalysis, precipitation data at 5-min intervals from automatic weather stations over mainland China, and the best track data of TS Bilis (2006). The results show that the simultaneous and 6-hour-lagged correlation coefficients between VWS and storm intensity (the minimum central sea level pressure) are 0.59145 and 0.57438 (P < 0.01), respectively. The averaged VWS was found to be about 11 m s−1 and thus suppressed the intensification of Bilis (2006). Distribution of precipitation in Bilis (2006) was highly asymmetric. The azimuthally-averaged rainfall rate in the partial eyewall, however, was smaller than that in a major outer rainband. As the storm intensified, the major rainband showed an unusual outward propagation. The VWS had a great impact on the asymmetric distribution of precipitation. Consistent with previous modeling studies, heavy rainfall generally occurred downshear to downshear-left of the VWS vector both near and outside the eyewall, showing a strong wavenumber-one asymmetry, which was amplified as the VWS increased.

Rainfall prediction remains one of the most challenging problems in weather forecasting. In order to improve high-resolution quantitative precipitation forecasts (QPF), a new procedure for assimilating rainfall rate derived from radar composite reflectivity has been proposed and tested in a numerical simulation of the Chicago floods of 17–18 July 1996. The methodology is based on the one-dimensional variation scheme (1DVAR) assimilation approach introduced by Fillion and Errico but applied here using the Kain-Fritsch convective parameterization scheme (KF CPS). The novel feature of this work is the continuous assimilation of radar estimated rain rate over a three hour period, rather than a single assimilation at the initial (analysis) time. Most of the characteristics of this precipitation event, including the propagation, regeneration of mesoscale convective systems, the frontal boundary across the Midwest and the evolution of the low-level jet are better captured in the simulation as the radar-estimated precipitation rate is assimilated. The results indicate that precipitation assimilation during the early stage can improve the simulated mesoscale feature of the convection system and shorten the spin-up time significantly. Comparison of precipitation forecasts between the experiments with and without the 1DVAR indicates that the 1DVAR scheme has a positive impact on the QPF up to 36 hours in terms of the bias and bias equalized threat scores.

The knowledge of the ratio of rain attenuation at one frequency to that at another on slant paths is useful for the design of satellite-to-Earth communication links and up-link power control systems. It is well known that the rain attenuation is influenced by parameters of precipitation along the slant path such as DSD (raindrop size distribution), raindrop temperature, rainfall rate, and so on. In this paper, based on several DSDs applied to various climate zones, at short microwave and long millimeter wave bands, the attenuation ratios are estimated on Earth-space paths. A comparison of the prediction results with the experiment data in Boston and Kashima areas is carried out. It is shown that the M-P and Weibull DSD applied to rain attenuation ratios estimation are better DSD at higher latitude regions. The Guangzhou DSD applied to rain attenuation ratios prediction is better in tropical and subtropical areas in China. The lognormal DSD may be a appropriate DSD applied to predict rain attenuation ratios in tropical areas at Adown>1dB or R>15mm/h. However, the attenuation ratios predicted by the Guangzhou DSD disagree with by the lognormal DSD, it requires that the DSD applied to predict rain attenuation ratios are further studied in tropical areas.

Numerical simulations of two heavy rainfall cases in the Changjiang-Huaihe River basin are performed with TRMM/PR (precipitation radar) data incorporated into the PSU/NCAR meso scale model MM5. The mixing ratio of rainwater q r is obtained from the R −q r relation (R is the rainfall rate), and the mixing ratio of water vapor q v in the model is replaced by q 1′v = q v+q r. Then, TRMM/PR data are used to modify humidity analysis obtained from conventional radiosonde data, and sensitivity experiments (STE) are performed and compared to control experiments (CTL). Results show that both the heavy rainfall distribution and its maximum amounts from STE are improved compared with those from CTL.

Two microwave radiative transfer models of precipitating cloud are used to simulate the microwave upwelling radiances emerging from precipitating clouds. Comparison of the simulation results shows that significant difference of microwave upwelling radiances exists between these two radiative transfer models. Analysis of these differences in different cloud and precipitation conditions shows that it is complicated but has certain trend for different microwave frequencies. The results may be useful to quantitative rainfall rate retrieval of real precipitating clouds.

In order to derive some statistical rainfall characteristics applicable to hydrology, data of continuous rainfall rate recordings of a Jardi gauge installed in Barcelona (Spain) have been converted to an hourly precipitation series. From these data, four useful distributions have been obtained and further compared with some theoretical models. It has been found that the duration of events is distributed exponentially. The duration of rainless intervals follow a generalized Pareto distribution, and the cumulative rainfall in the cumulative rain duration is beta distributed. Concerning the distribution of rain amounts, two models can be accepted, depending on the duration of the events. Comparison with a similar study carried out in Farnborough (United Kingdom) indicates that the events are shorter and that the amounts of rain collected in short events are larger in Barcelona.

The Kuo-type cumulus parameterization and rainfall rate scheme is extended by including the outgoing longwave radiation (OLR), the local time rate of change of OLR, and the horizontal Laplacian of OLR to include the additional source of mesoscale moisture supply. The extended scheme remains simple and efficient. A series of 5-day forecasts of the 1979 monsoon for the tropical belt between the Arabian Sea and the western Pacific Ocean show improvement in the 3-day forecast in the daily accumulated precipitation in both the amount and location. Further RMS error analyses indicate that using OLR and the Laplacian of OLR also produces a significant improvement in a 3-day forecast. Additional tests of the extended scheme for the 1987 and 1988 monsoons produced consistent and characteristic areal rainfall rates in the tropics. The improvement in the “OLR model” forecasts is attributed to the improved skill of OLR forecast in the forecast model as the RMS errors for 5 consecutive days in the 6 experimental forecasts are smaller than those of the 3 control forecasts.

As a natural tracer the cosmic-rayproduced 7Be has proven to be useful for studying atmospheric transport mechanisms. It is well known that the concentration of 7Be in ground level air and precipitation shows seasonal variations. Feely et. al. [1] reported that the variations in the concentration of 7Be are due to at least four factors: the rate of exchange between the stratosphere and the troposphere, the rate of vertical mixing within the troposphere, the transport of air masses from middle to higher latitudes, and variations in the rainfall rate. We have determined at Munich-Neuherberg the seasonal variations of the 7Be concentrations [2, 8] and the long-term variations of the an

Five years of comprehensive research on precipitation structures showed that the time bases and the design of the measuring equipment are most important for statistical measure of precipitation parameters. The influence of different methods, and different time bases as determined by calculations based on measurements are presented. Small differences on the time scale produce large errors (e.g. more than 100 %in rainfall rate).

A large sample of summertime data from the McGill Radar Weather Observatory was analyzed to determine the variation with altitude of the horizontal extent of individual rainshowers. For echoes defined by a reflectivity factor of 39 dBz (equivalent to a rainfall rate of about 10 mm/h) it was found that the mean area of the total population of echoes decreases linearly with altitude from approximately 20 km2 at 2 km to 11 km2 at 8 km. Subsets of the total population were investigated, consisting of only the echoes penetrating the altitudes of 6, 7, and 8 km. On the average these relatively tall echoes are much greater in horizontal extent than the total population. Whereas the sizes of the total population of echoes at any altitude are distributed approximately exponentially in terms of the square root of area, the sizes of the “survivors” that extend to high altitudes may be described by the gamma distribution with a mean value decreasing approximately linearly with height above 3 km and a dispersion of 0.55. Some characteristics are also reported for echoes defined by reflectivities of 31 dBz and 47 dBz. Estimates are given of the fraction of the total area in a horizontal plane that contains echoes in each of these categories.

The rain dropsize distributions measured by a disdrometer in 21 rain events consisting of 1, 640one-minute dropsize spectra have been analyzed for a tropical station, Ile-Ife (geog. lat. 7.5°N, long 4.5°E) in South-Western Nigeria. Empirical power law relations of the form Y = aRb have been obtained between the rainfall rate R, the radar reflectivity factor Z, liquid water content M, optical extinction σ and the median volume diameter D0 for three types of rainfall. A power law relationship was also obtained between the median volume diameter D0 and the liquid water content M. The variability in a and b with rain parameters, rain events and rain types is discussed. The empirical relations have been compared with existing relations for other parts of the world, for their utilization in radar meteorology and radar engineering.

This paper deals with a method for estimating rain attenuation distribution at frequencies above 10 GHz. This method depends only on point rainfall rate. Based on statistical independence among rain cells, a relation connecting cell dimension, path distance, precipitation and attenuation is established. Numerical results have shown good agreement with experimental data.