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  • Understanding Diurnal Variability of Precipitation through Observations and Models (UDVPOM) x
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T. N. Krishnamurti, C. Gnanaseelan, A. K. Mishra, and A. Chakraborty

Sanjay 2003 ). It is possible to use these weights and construct a single forecast model that uses a weighted average (based on these weights) for a unified model. Such a unified model was shown to carry a skill higher than those of the member models and their ensemble mean but lower than a multimodel superensemble. These results are shown in Figs. 1 and 2 for days 1 and 2 of rainfall forecasts over the global tropics, North America, and the Asian monsoon domain. In a related study, Chakraborty

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Arindam Chakraborty and T. N. Krishnamurti

phase of convective precipitation over both land and oceans. The phases, however, show wide variations over different parts of the tropics ( Shin et al. 1990 ; Janowiak et al. 2005 ; Yang and Smith 2006 ). In general, precipitation over land (oceans) shows an afternoon (early morning) maximum (e.g., Dai 2001 ). This is primarily due to the fact that the thermal capacity of land is less compared to the ocean. Therefore, land is heated up faster by solar radiation in daytime. This leads to

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Munehisa K. Yamamoto, Fumie A. Furuzawa, Atsushi Higuchi, and Kenji Nakamura

those from PR over the summer tropics (winter midlatitude). Errors arise because of 1) the underestimation of TMI precipitation water path by TMI in midlatitudes, 2) the underestimation of near-surface precipitation water content by PR in tropics ( Masunaga et al. 2002 ), 3) errors of TMI rain estimates depending on storm height and rain type ( Furuzawa and Nakamura 2005 ), 4) errors in the TMI algorithm freezing-level assumption, or inadequate radar-reflectivity factor to rainfall rate ( Z – R

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Song Yang and Eric A. Smith

attenuation and scattering ( Kummerow et al. 1998 ). To date, TRMM has provided reliable, continuous, and accurate rain-rate estimates based on various physical algorithms over the global tropics and subtropics that have led to a greater understanding of precipitation processes and variability ( Kummerow et al. 2000 ; Wolff et al. 2005 ; Yang and Smith 2006 ; Yang et al. 2006a , b ; E. A. Smith et al. 2008, unpublished manuscript; Yang et al. 2008 ). Classifying precipitation into convective and

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Alex C. Ruane and John O. Roads

temperature than occur over the ocean. Annual variance in the tropics is dominated by the converging portion of the Hadley circulation, which draws moist lower-tropospheric air into the ITCZ. Both P ′ and E ′ have a dynamic Hadley signature, with tropical precipitation dominated by convergence ( Fig. 5c ) and subtropical evaporation over the oceans corresponding to the diverging regions underneath the descending portions of the circulation ( Fig. 5f ). Many of the annual behaviors occur on land as well

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Donald Wylie

summaries of global cloud cover and is broken into the opposite seasons of boreal summer (June–August) and boreal winter (December–February). Clouds are most frequent in the tropics especially over South America and Africa. This is the intertropical convergence zone (ITCZ), which moves north and south with the seasons. Clouds are less frequent north and south of the ITCZ, which is where the subtropical deserts occur over land and the subtropical high pressure centers occur over oceans. Frequent cloud

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Song Yang, Kwo-Sen Kuo, and Eric A. Smith

at specific grid regions. It is seen that at the 5° × 5° spatial scale, a few oceanic grid locations exhibit dominant postnoon maxima, while a few continental grid locations indicate dominant prenoon maxima. The reasons for these exceptions deserve future examination. In addition, close examination of the clock faces reveals that secondary maxima (denoted by light gray inner faces) are widespread throughout the tropics and subtropics observed by the TRMM satellite, in which secondary postnoon

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R. Cifelli, S. W. Nesbitt, S. A. Rutledge, W. A. Petersen, and S. Yuter

field campaigns were conducted: the East Pacific Investigation of Climate Processes in the Coupled Ocean–Atmosphere System (EPIC-2001; Raymond et al. 2004 ) and the Tropical Eastern Pacific Process Study (TEPPS; Yuter and Houze 2000 ). Precipitation diurnal variations in the tropics have been studied extensively (e.g., Gray and Jacobson 1977 ; Hendon and Woodberry 1993 ; Garreaud and Wallace 1997 ; Chen et al. 1996 ; Sui et al. 1997 ; Dai 2001 ; Yang and Slingo 2001 ; Bowman et al. 2005

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R. E. Carbone and J. D. Tuttle

inland over a 5-h period (1700–2200 UTC) at a mean rate of 14 m s −1 . Because there are no meridional steering winds of this magnitude, it is speculated that mesoscale cold pool dynamics drive this propagation in a manner similar to that observed under breeze conditions elsewhere in the tropics (e.g., Carbone et al. 2000 ). The remaining feature of note in Fig. 11 is the nocturnal maximum from 35° to 45°N. The small maximum frequency between 37° and 39°N and between 1200 and 1400 UTC is most

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Tianjun Zhou, Rucong Yu, Haoming Chen, Aiguo Dai, and Yang Pan

. Meteor. Soc. , 84 , 1205 – 1217 . Wallace , J. M. , 1975 : Diurnal variations in precipitation and thunderstorm frequency over the conterminous United States. Mon. Wea. Rev. , 103 , 406 – 419 . Yang , G-Y. , and J. Slingo , 2001 : The diurnal cycle in the tropics. Mon. Wea. Rev. , 129 , 784 – 801 . Yang , S. , and E. A. Smith , 2006 : Mechanisms for diurnal variability of global tropical rainfall observed from TRMM. J. Climate , 19 , 5190 – 5226 . Yeh , D. Z. , and Y. X

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