Global Precipitation: Means, Variations and Trends During the Satellite Era (Invited)
Abstract
Global precipitation amounts and patterns are summarized in terms of the global mean absolute value (with error bar) and inter-annual and inter-decadal variations and trends, using the Global Precipitation Climatology Project (GPCP) analyses, with comparison to TRMM, Cloudsat and other recent satellite observations. The GPCP monthly product (1979-present), a combined analysis based on various passive microwave and infrared satellite-based estimates and gauge measurements over land, is an often-used standard estimate of global precipitation. For global and regional water (and energy) balance studies the absolute magnitude of precipitation is important. Although the current GPCP analyses do not include newer data such as TRMM (passive microwave and precipitation radar), Cloudsat (cloud radar), and AMSR (passive microwave), comparison with these more modern data confirm the earlier GPCP estimates of magnitude in terms of tropical ocean and global ocean areas, where, unlike over land, we have to rely on the satellite remote sensing for absolute values. During the last 30 years inter-annual variations of global total precipitation can be detected with small increases (a few percent) occurring during El Ninos and decreases (up to ~4%) related to effects of volcanoes. Inter-annual patterns of precipitation variation are also quite evident, especially with ENSO events. During this 30-year period global surface temperature has increased due to global warming along with an increase in atmospheric water vapor, with a Clausius-Clapeyron (~7%/C) rate. However, global precipitation (according to the GPCP analyses) has increased only slightly, if at all (0-2 %/C). This weaker relation global temperature and precipitation is in agreement with theory and climate model simulations. However, there are significant patterns of positive and negative trends in precipitation across the globe during the period. However, it also is noted that a 'climate shift' has occurred at about 1998-2000 that is clearly evident in the global surface temperature and atmospheric water vapor records, with a nearly flat time history after the turn of the century. This 'shift' appears to be an inter-decadal variation related to the Pacific Decadal Variation (PDV). No clearly discernible 'shift' is evident in the global total precipitation record, although the pattern of change in the observations during the satellite era is shown to have both a global warming signature and a PDV-related signal during the last 30 years. During the last 15 years the set of passive microwave satellites combined with the Precipitation Radar on TRMM has allowed for analysis of precipitation on a quasi-global basis down to daily and 3-hr resolution which has led to the first efforts at using satellite information to produce a 'climatology' of extreme precipitation and begin to examine variations in heavy rainfall across the globe with satellite data. The near-future of all these efforts will be enhanced by the Global Precipitation Measurement (GPM) mission set to launch in a few months and further development and flight of other research and operational satellite precipitation instruments.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.U44A..03A
- Keywords:
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- 1640 GLOBAL CHANGE Remote sensing;
- 3354 ATMOSPHERIC PROCESSES Precipitation;
- 1833 HYDROLOGY Hydroclimatology