Precipitation

About: Precipitation is a research topic. Over the lifetime, 32861 publications have been published within this topic receiving 990496 citations. The topic is also known as: rain & rainfall.

Monsoon precipitation in the AMIP runs

Abstract: We present an analysis of the seasonal precipitation associated with the African, Indian and the Australian-Indonesian monsoon and the interannual variation of the Indian monsoon simulated by 30 atmospheric general circulation models undertaken as a special diagnostic subproject of the Atmospheric Model Intercomparison Project (AMIP) The seasonal migration of the major rainbelt observed over the African region, is reasonably well simulated by almost all the models The Asia West Pacific region is more complex because of the presence of warm oceans equatorward of heated continents Whereas some models simulate the observed seasonal migration of the primary rainbelt, in several others this rainbelt remains over the equatorial oceans in all seasons Thus, the models fall into two distinct classes on the basis of the seasonal variation of the major rainbelt over the Asia West Pacific sector, the first (class I) are models with a realistic simulation of the seasonal migration and the major rainbelt over the continent in the boreal summer; and the second (class II) are models with a smaller amplitude of seasonal migration than observed The mean rainfall pattern over the Indian region for July-August (the peak monsoon months) is even more complex because, in addition to the primary rainbelt over the Indian monsoon zone (the monsoon rainbelt) and the secondary one over the equatorial Indian ocean, another zone with significant rainfall occurs over the foothills of Himalayas just north of the monsoon zone Eleven models simulate the monsoon rainbelt reasonably realistically Of these, in the simulations of five belonging to class I, the monsoon rainbelt over India in the summer is a manifestation of the seasonal migration of the planetary scale system However in those belonging to class II it is associated with a more localised system In several models, the oceanic rainbelt dominates the continental one On the whole, the skill in simulation of excess/deficit summer monsoon rainfall over the Indian region is found to be much larger for models of class I than II, particularly for the ENSO associated seasons Thus, the classification based on seasonal mean patterns is found to be useful for interpreting the simulation of interannual variation The mean rainfall pattern of models of class I is closer to the observed and has a higher pattern correlation coefficient than that of class II This supports Sperber and Palmer’s (1996) result of the association of better simulation of interannual variability with better simulation of the mean rainfall pattern The hypothesis, that the skill of simulation of the interannual variation of the all-India monsoon rainfall in association with ENSO depends upon the skill of simulation of the seasonal variation over the Asia West Pacific sector, is supported by a case in which we have two versions of the model where NCEP1 is in class II and NCEP2 is in class I The simulation of the interannual variation of the local response over the central Pacific as well as the all-India monsoon rainfall are good for NCEP2 and poor for NCEP1 Our results suggest that when the model climatology is reasonably close to observations, to achieve a realistic simulation of the interannual variation of all-India monsoon rainfall associated with ENSO, the focus should be on improvement of the simulation of the seasonal variation over the Asia West Pacific sector rather than further improvement of the simulation of the mean rainfall pattern over the Indian region

Circulation effect: response of precipitation δ18O to the ENSO cycle in monsoon regions of China

Abstract: Inter-annual variation in the ratio of 18O to 16O of precipitation (δ18Op) in the monsoon regions of China (MRC, area approximately east of 100°E) has not yet been fully analyzed. Based on an analysis of the relationships between the time series of amount-weighted mean annual δ18O in precipitation (δ18Ow) and meteorological variables such as temperature, precipitation as well as atmospheric/oceanic circulation indices, it is recognized that the El Nino-Southern Oscillation (ENSO) cycle appears to be the dominant control on the inter-annual variation in δ18Op in the MRC. Further analysis shows that the trade wind plays a role in governing δ18Ow through affecting the intensity of the different summer monsoon circulations which are closely linked to the weakening (weaker than normal) and strengthening (stronger than normal) of the trade wind and gives the δ18Ow different values at or over inter-annual timescales. The southwest monsoon (SWM) drives long-distance transport of water vapor from Indian Ocean to the MRC, and along this pathway increasing rainout leads to more negative δ18Ow via Rayleigh distillation processes. In contrast, the southeast monsoon (SEM), which is consistent with the changes in the strength of the West Pacific subtropical high, drives short-distance water vapor transport from the West Pacific Ocean to the MRC and leads to less negative δ18Ow. Therefore, the δ18Ow value directly reflects the differences in influence between the SWM, which is strong when the SE trade wind is strong, and the SEM, which is strong when the SE trade wind is weak. In addition, the South China Sea Monsoon also transports local water vapor as well as plays a role in achieving the synchronization between the δ18Ow and ENSO. The author thus terms the δ18Op rhythm in the MRC the “circulation effect”. In turn, the δ18Op variation in the MRC has the potential to provide information on atmospheric circulation and the signal of δ18Op recorded in natural archives can then be used to deduce a long-term behavior of the tropical climate system.

Sensitivity of tropical precipitation extremes to climate change

Abstract: Precipitation extremes increase in intensity over many regions of the globe in simulations of a warming climate, but not always consistently. Observational constraints, together with a close relationship between model responses to interannual variability and climate change, suggest a high sensitivity of tropical extreme precipitation to warming.

Bias corrections of long‐term (1973–2004) daily precipitation data over the northern regions

Abstract: [1] A consistent daily bias correction procedure was applied at 4802 stations over high latitude regions (North of 45°N) to quantify the precipitation gauge measurement biases of wind-induced undercatch, wetting losses, and trace amount of precipitation for the last 30 years. These corrections have increased the gauge-measured monthly precipitation significantly by up to 22 mm for winter months, and slightly by about 5 mm during summer season. Relatively, the correction factors (CF) are small in summer (10%), and very large in winter (80–120%) because of the increased effect of wind on gauge undercatch of snowfall. The CFs also vary over space particularly in snowfall season. Significant CF differences were found across the USA/Canada borders mainly due to differences in catch efficiency between the national gauges. Bias corrections generally enhance monthly precipitation trends by 5–20%. These results point to a need to review our current understanding of the Arctic fresh water budget and its change.

Geochemical studies of the Weddell sea

Abstract: The origin of Antarctic Bottom Water is discussed in terms of the distributions of a number of geochemical tracers in the major water masses of the Weddell Sea. Oxygen, phosphate, nitrate and total inorgabic carbon are shown to be negligibly altered by consumption or production during sub-surface circulation and mixing. All the conservative properties of Weddell Sea Bottom Water and Antarctic Bottom Water are explained as simple mixtures of Winter Water, Warm Deep Water, and Western Shelf Water. Silica is markedly non-conservative, showing enrichments up to ≈35 μM kg−1 which are due mainly to interactions with the bottom. The deuterium and oxygen-18 stable isotope data show that the high salinity of Western Shelf Water is principally the result of freezing rather than evaporation. The isotopic composition of Western Shelf Water also requires a significant admixture of melt-water from the base of the Filchner Ice Shelf, and mass-balance calculations linking the rate of shelf ice melting to the formation of bottom water give a production rate of about 5 × 106 m3 s−1 for Weddell Sea Bottom Water with potentiatial −0.9°C, or about 8 × 106 m3 s−1 in terms of classical Antarctic Bottom Water with a potential temperature of −0.4°C. Concentrations of the radioisotopes carbon-14 and tritium are exceptionally low in the Weddell Sea despite the fact that the CO2 atmospheric exchange rate is comparable to the global average. The low values are seen to be the result of a short surface residence time, a large sub-surface mixing component, and exchange inhibition by sea ice especially during the winter. Unlike the average world ocean, where molecular exchange is about three times more important than precipitation in transporting atmospheric tritium to surface waters, about four times more tritium is added to the Weddell Sea by precipitation than by molecular exchange. The flux of new Weddell Sea Bottom Water based on the tritium data is estimated very roughly at about 3 × 106 m3 s−1, or about 4.5 × 106 m3 s−1 expressed in terms of classical Antarctic Bottom Water.