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R. E. Carbone and J. D. Tuttle

1. Introduction Many aspects of the earth’s water cycle are not well understood and precipitation is not well simulated by climate system models. Convective precipitation is especially problematic, including convection organized at the large mesoscale. Numerous studies have employed diurnal variability as a framework from which to improve the understanding of water cycle forcings and to serve as a benchmark for new representations in models. This study examines the diurnal cycle of warm

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Alex C. Ruane and John O. Roads

1. Introduction Nearly all atmospheric activity is originally derived from external solar forcing. On time scales of a year and less, this forcing arrives in the form of a strong daily signal resulting from the rotation of the earth and a seasonal signal due to the earth’s orbit and inclination. The diurnal and annual cycles of solar insolation are therefore fundamental to the earth’s water cycle, but do not necessarily drive an equivalent response. Energy from these solar forcings interacts

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

; and many others). A number of forcing mechanisms have been proposed to account for the diurnal cycle (see Yang and Smith 2006 for a recent literature review). The majority of observational studies, using data ranging from rain gauge and ship reports to radar and satellite data, have shown that precipitation diurnal variations are pronounced over land during the warm season, with a maximum in precipitation occurring in the late afternoon–early evening occurring in most (but not all) areas

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J. Li, S. Sorooshian, W. Higgins, X. Gao, B. Imam, and K. Hsu

model ( Chen and Dudhia 2001 ). The vertical coordinate of MM5 is a terrain-following coordinate system. In this study, 31 vertical sigma layers were employed from the surface to the top of atmosphere at 100 mb. The operational NCEP Eta Model 212 grid (40 km) model analysis data for July and August 2004 were used as forcing fields. The Eta Model analysis data were used as model initial conditions and model boundary conditions in all tests. The model was initialized at 0000 UTC and integrated up to

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

precipitation as a global phenomenon. Yang and Smith (2006) provide a detailed review and analysis of the variety of mechanisms controlling the diurnal cycle of precipitation. Based on the use of TRMM precipitation data, their analysis demonstrated that diurnal precipitation variability is a global phenomenon with embedded diurnal forcing factors, which are far more complex than can be explained with a few general causes (i.e., the approach followed by nearly all past literature concerning this topic

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Song Yang and Eric A. Smith

) interaction. This is a synoptic-scale mechanism that presumes that enhanced cloud-top IR cooling at night, stemming from the lack of cloud-top solar absorption, and a consequent increase in the thermal lapse rate ( Kraus 1963 ; Lavoie 1963 ; Ramage 1971 ), leads to stronger convection and nighttime rainfall. The SRC mechanism enables radiative forcing to favor more intense rainfall during the late night period, provided a there is a preexistence of cloudiness. The problems with this mechanism in

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

, C. Akoshile , J. Janowiak , and P. Arkin , 2006 : Diurnal and seasonal variability of rainfall in the sub-Sahel as seen from observations, satellites and a numerical model. Geophys. Res. Lett. , 33 . L07806, doi:10.1029/2005GL025192 . Qian , T. , A. Dai , K. E. Trenberth , and K. W. Oleson , 2006 : Simulation of global land surface conditions from 1948–2004. Part I: Forcing data and evaluation. J. Hydrometeor. , 7 , 953 – 975 . Shinoda , M. , T. Okatani , and M

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