Diurnal cycle of tropical precipitation in Tropical Rainfall Measuring Mission (TRMM) satellite and ocean buoy rain gauge data

Abstract

[1] The climatological diurnal cycle of precipitation in the tropics is analyzed using data from rain gauges on ocean buoys and satellite measurements by the Tropical Rainfall Measuring Mission (TRMM) satellite. The ocean buoy data are from the NOAA/Pacific Marine Environmental Laboratory Tropical Atmosphere-Ocean/Triangle Trans-Ocean buoy Network in the tropical Pacific Ocean. TRMM data are from the precipitation radar (PR) and the TRMM microwave imager (TMI). Climatological hourly mean precipitation rates are analyzed in terms of the diurnal and semidiurnal harmonics. Both data sets confirm an early morning peak in precipitation over ocean regions. The amplitude of the diurnal harmonic over the oceans is typically less than 25% of the mean precipitation rate. Over tropical land masses the rainfall peaks in the afternoon and evening hours. The relative amplitude of the diurnal harmonic over land is larger than over the ocean, often exceeding 50% of the mean rain rate. Previously noted differences between the TMI and PR rainfall retrievals persist in the diurnal cycle. On average the TMI measures more rainfall than the PR and has a larger diurnal variation. Phase differences between the two instruments do not show a consistent bias.

Diurnal Variation of Summer Rainfall over the Tibetan Plateau and Its Neighboring Regions Revealed by TRMM Multi‐Satellite Precipitation Analysis

“…Using the precipitation data from TRMM (Tropical Rainfall Measuring Mission) satellite, Nesbitt and Zipser [3] found that over oceans, the diurnal cycle of rainfall has a small amplitude and the maximum contribution to total rainfall from meso-scale convective E-mail: baiaj@ieecas.cn systems appears in the early morning, but land areas have a more significant diurnal cycle than oceans, with a minimum in the mid-morning and a maximum in the afternoon. Using the buoys data on oceans Bowman et al [5] confirmed the foregoing conclusions [2,3] .…”

The Surface Diurnal Warm Layer in the Indian Ocean during CINDY/DYNAMO

“…Typically, the diurnal cycle of precipitation over the tropical open ocean is weak, with a peak before sunrise (Gray and Jacobson 1977;Bowman et al 2005). However, during periods of high solar radiation and weak winds, as well as a strong diurnal SST cycle, atmospheric convection over the ocean can behave similarly to that over land, with a strong diurnal cycle, growth of cumulus congestus, and a precipitation maximum in the late evening (Johnson et al 1999).…”

Intra-seasonal variability of cloud amount over the Indian subcontinent during the monsoon season as observed by TRMM precipitation radar

“…To address the geographical inhomogeneity of sampling, these composite data counts for each cloud type are normalized by dividing convective and stratiform pixel count of a grid box by the total scan pixel count of that grid box and multiplying by 100 to get the percentage value of convective / stratiform fraction of that grid box. Since these phases are spread over nine years, the diurnal bias in the sampling is also another likely source of error (Negri et al, 2002 andBowman et al, 2005). We expect the benefits of having such a high-resolution dataset to outweigh the disadvantage of some statistical fluctuations since the horizontal gradients and temporal scale of precipitation over this region during the monsoon season, are probably much larger than the sampling errors (Anders et al, 2006;Romatschke and Houze, 2011).…”