Climatic characteristics of convective and stratiform precipitation over the Tropical and Subtropical areas as derived from TRMM PR

Climatic characteristics of convective and stratiform precipitation over the Tropical and Subtropical areas are investigated based on the measurements of Tropical Rainfall Measuring Mission's(TRMM) Precipitation Radar(PR) from 1998 to 2007.Results indicate that convective precipitation are distributed mainly over the Intertropical Convergence Zone(ITCZ),the South Pacific Convergence Zone(SPCZ),the Asian Monsoon Region,regions between the South America and the Mid-America,and the Tropical Africa where the frequencies lie between 1% and 2%.But in four seasons,total area fractions of convective precipitation frequencies less than 1% all exceed 85%.The frequencies of stratiform precipitation are much higher than those of convective precipitation,and total area fractions of stratiform precipitation frequencies >1% are over 55% during four seasons.However,frequencies of the two rain types show not only remarkable regionality,but also distinct seasonal variations.Conditional rain rates of convective precipitation range from 6 to 14 mm/h whereas those of stratiform precipitation are smaller than 4 mm/h.Meanwhile,rain tops of convective precipitation are higher than those of stratiform precipitation.The mean profiles of the two rain types show significant latitudinal dependency.And the seasonal variations of precipitation profiles are displayed mainly in the variations of rain tops.The frequencies and conditional rain rates of both rain types over ocean are higher than those over land,but rain tops are just the opposite.Moreover,the seasonal variations of both rain types over ocean are weaker than those over land because of the different stable states of underlying surfaces.

Seasonal variability in tropical and subtropical convective and stratiform precipitation of the East Asian monsoon

Seasonal variations in tropical and subtropical convective and stratiform precipitation of the East Asian monsoon are analyzed using 10-year (1998-2007) Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) rain products (2A25). Datasets from the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) 24 general circulation models (GCMs) are evaluated using TRMM PR rain products in terms of their ability to simulate convective and stratiform precipitation and their deficiencies. The results show that Asian monsoon convective and stratiform precipitation increases significantly after onset of the summer monsoon, but the percentage of convective precipitation clearly decreases over tropical areas while it increases in subtropical regions. The GCMs simulate well the seasonal variation in the contribution of Asian monsoon subtropical convective precipitation to the total rainfall; however, the simulated convective precipitation amount is high while the simulated stratiform precipitation amount is low relative to TRMM measurements, especially over the Asian monsoon tropical region. There is simultaneous TRMM-observed convective and stratiform precipitation in space and time, but GCMs cannot simulate this relationship between convective and stratiform precipitation, resulting in the deficiency of stratiform precipitation simulations.

Numerical Simulation on the Rainout-Removal of Sulfur Dioxide and Acidification of Precipitation from Stratiform Clouds

The rainout-removal of SO2 and the acidification of precipitation from stratiform clouds are simulated using a one-dimensional, time-dependent model, parameterized microphysically in which dissolution and dissociation of gaseous SO2 and H2O2, and oxidation reaction in aqueous phase are taken into account. The effects of dynamic factors, including updraft flow and turbulent transport, and the concentration of gaseous SO2 and H2O2 being transported into the clouds on pH value of the precipitation, the conversion rate S(Ⅳ)-S(Ⅵ) and the wet deposition rate of SO2 are discussed.

Precipitation Evolution from Plain to Mountains during the July 2023 Extreme Heavy Rainfall Event in North China

North China experienced devastating rainfall from 29 July to 1 August 2023,which caused substantial flooding and damage.This study analyzed observations from surface rain gauges and S-band dual-polarization radars to reveal the following unique features of the precipitation evolution from the plain to the mountains during this event.(1) The total rainfall was found concentrated along the Taihang Mountains at elevations generally > 200 m,and its spatiotemporal evolution was closely associated with northward-moving low-level jets.(2) Storms propagated northwestward with southeasterly steering winds,producing continuous rainfall along the eastern slopes of the Taihang Mountains owing to mountain blocking,which resulted in the formation of local centers of precipitation maxima.However,most rainfall episodes with an extreme hourly rainfall rate(HRR),corresponding to large horizontal wind shear at low levels,actively occurred in the plain area to the east of the Taihang Mountains.(3) The western portion of the extreme heavy rain belt in the north was mainly caused by long-lasting cumulus–stratus mixed precipitation with HRR< 20 mm h~(-1);the eastern portion was dominated by short-duration convective precipitation with HRR > 20 mm h~(-1).The contributions of convective precipitation and cumulus–stratus mixed precipitation to the total rainfall of the southern and middle rain belts were broadly equivalent.(4) The local HRR maxima located at the transition zone from the plain to the mountains were induced by moderate storm-scale convective cells with active warm-rain processes and large number of small-sized rain droplets.(5) During the devastating rainfall event,it was observed that the rainfall peaked at around 1800 local time(LT) every day over the upstream plain area(no diurnal cycle of rainfall was observed in relation to the accumulated rainfall centers over mountain areas).This was attributable to convective activities along the storm propagation path,which was a result of the more unstable stratification with a suitable steering mechanism that was related to afternoon solar heating and enhanced water vapor.The findings of this study improve our understanding and knowledge of the extreme precipitation that can develop from the plain to the mountains in North China.