TRMM Radar Observations of Shallow Precipitation over the Tropical Oceans

Short, David; Nakamura, Kenji

doi:10.1175/1520-0442(2000)013<4107:troosp>2.0.co;2

Cited by 164 publications

(144 citation statements)

References 69 publications

(72 reference statements)

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“…Measurements from the precipitation radar (PR) deployed during the Tropical Rainfall Measuring Mission (TRMM, 1997(TRMM, -2015 first emphasized the prevalence of warm rain over global oceans and their potential impact on large-scale heating rates (Short and Nakamura 2000;Schumacher and Houze 2003;Takayabu et al 2010). But the TRMM PR has a minimum detection threshold of about 0.4-0:5 mm h À1 and therefore misses about 9% of accumulated rain and up to 50% of the occurrence of light rain compared to CloudSat (Berg et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Implications of Warm Rain in Shallow Cumulus and Congestus Clouds for Large-Scale Circulations

et al. 2017

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Space-borne observations reveal that 20-40% of marine convective clouds below the freezing level produce rain. In this paper we speculate what the prevalence of warm rain might imply for convection and large-scale circulations over tropical oceans. We present results using a two-column radiative-convective model of hydrostatic, nonlinear flow on a non-rotating sphere, with parameterized convection and radiation, and review ongoing efforts in high-resolution modeling and observations of warm rain. The model experiments investigate the response of convection and circulation to sea surface temperature (SST) gradients between the columns and to changes in a parameter that controls the conversion of cloud condensate to rain. Convection over the cold ocean collapses to a shallow mode with tops near 850 hPa, but a congestus mode with tops near 600 hPa can develop at small SST differences when warm rain formation is more efficient. Here, interactive radiation and the response of the circulation are crucial: along with congestus a deeper moist layer develops, which leads to less low-level radiative cooling, a smaller buoyancy gradient between the columns, and therefore a weaker circulation and less subsidence over the cold ocean. The congestus mode is accompanied with more surface precipitation in the subsiding column and less surface precipitation in the deep convecting column. For the shallow mode over colder oceans, circulations also weaken with more efficient warm rain formation, but only marginally. Here, more warm rain reduces convective tops and the boundary layer depth-similar to Large-Eddy Simulation (LES) studies-which reduces the integrated buoyancy gradient. Elucidating the impact of warm rain can benefit from large-domain high-resolution simulations and observations. Parameterizations of warm rain may be constrained through collocated cloud and rain profiling from ground, and concurrent changes in convection and rain in subsiding and & Louise Nuijens

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Section: Introductionmentioning

confidence: 99%

Implications of Warm Rain in Shallow Cumulus and Congestus Clouds for Large-Scale Circulations

et al. 2017

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“…A breakthrough was brought by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR). The TRMM PR, capable of profiling the vertical precip itation structure, has been proved to be useful for illustrating the global climatology of shallow precip itation as well as more developed systems with higher radar-echo tops (Short and Nakamura 2000). The TRMM PR, however, is less sensitive to frozen hydro meteors than to rain drops of the same size, so that a considerable amount of ice particles aloft could be left undetected (Masunaga et al 2002).…”

Section: Introductionmentioning

confidence: 99%

A 9-season TRMM Observation of the Austral Summer MJO and Low-frequency Equatorial Waves

Masunaga

2009

Journal of the Meteorological Society of Japan

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A long-term observation from the Tropical Rainfall Measuring Mission (TRMM) is analyzed to investigate the Madden-Julian Oscillation (MJO), Kelvin wave, and equatorial Rossby (ER) wave in austral summer seasons. TRMM Precipitation Radar (PR) and Visible/Infrared Scanner (VIRS) measurements are jointly used to clarify convective progression associated with individual modes of the tropical oscillations. Variability in the dynamic and thermodynamic environment involving sea surface temperature (SST), column relative humidity (CRH), and moisture convergence is also examined. A sea surface warming is found to precede the peak MJO convection by ~10 days, while a prior SST increase is not as evident for the Kelvin and ER waves. Moisture convergence and CRH exhibit a horseshoe-like pattern in the composite MJO map, constituted of a pair of off-equatorial maxima and a weak equatorial peak. The Kelvin wave has a moist anomaly on the equator leading the convective peak as theoretically expected, while the moist anomaly also extends poleward without being accompanied by moisture convergence. Moisture convergence leads CRH by a day or two for the Kelvin and ER waves. Moisture convergence is, in contrast, virtually concurrent with CRH for the MJO. The correlation between CRH and deep stratiform coverage is diverse among the three modes of the tropical oscillations. Shallow cumulus and cumulus congestus lead the MJO convective peak by ~1 day, followed by lingering non-precipitating high clouds. ER wave convection is led by moisture convergence but lagged by CRH. The convective progression appears not to proceed in a monotonic way for the ER wave.A possible mechanism to explain MJO propagation is discussed as suggested by a synthesis of the present findings. The Kelvin wave guides the eastward migration of MJO convection onset over the Indian Ocean. The role of the Kelvin wave in MJO propagation diminishes as the MJO enters the west Pacific with the convective area shifting away from the equator. Instead, the Kelvin wave convective heating induces poleward moisture transport and moistens the off-equatorial mid troposphere. The resultant moist anomaly is hypothesized to help trigger the MJO convective burst upon the arrival of ER wave disturbances. Such cooperative processes involving the Kelvin and ER waves could act as a driving engine of some, if not all, MJO episodes.

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“…Version 6 PR algorithms provided by the TRMM Science Team were used by TSDIS to calculate vertical profiles of radar reflectivity, near-surface rain rate (ℜ), storm top height and rain type, for each FOV. Data from 7 FOVs, nadir +/-3, were used to avoid issues with main-lobe contamination (Short and Nakamura 2000;hereafter SN) and FOVs that are tilted with-respect to the earth's surface.…”

Section: Datamentioning

confidence: 99%

An Interpretation of TRMM Radar Observations of Shallow Convection with a Rain Cell Model

Short

Hirose

Nakamura

2009

Journal of the Meteorological Society of Japan

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Observations of shallow, isolated convection from the Precipitation Radar (PR) aboard the Tropical Rainfall Measuring Mission (TRMM) observatory were compared with simulations from a rain cell model to examine effects of sub-resolution scale convection on space-borne radar observations. A large sample of shallow isolated convection was obtained from PR data over the central Pacific Intertropical Convergence Zone. Storm top heights, ranged from 1000 to 3750 m, with a mode at 1500 m. A secondary classification was made to identify 3 classes with progressively smaller spatial scales: groups of rainy fields-of-view (FOVs), rainy FOVs with one neighboring rainy FOV, and solitary rainy FOVs. Smaller spatial scales were associated with shallower storms and lower radar reflectivity (dBZ) values. The solitary class was the focus of the modeling comparison.The first objective of the modeling exercise was to explore the possibility that information on the horizontal scale and rain rate intensity of sub-resolution shallow convection could be extracted from the PR observations by finding an optimal fit between simulated and observed dBZ distributions. The height and diameter of simulated rain cells were linked by assuming an average aspect ratio of one. Simulated and observed probability distributions of dBZ were compared for two modes of rain cell variability: a fixed aspect ratio with variable cell dBZ, and a fixed cell dBZ with variable aspect ratio. Both modes resulted in excellent comparisons with observed distributions.The second modeling objective was to compare rain rates from the simulated "ground truth" and simulated "retrieved" rain rates, and to determine the effective sampling area of the modeled FOV. In general, simulated retrieved rain rates had a positive bias, as expected from the non-linear Z-R relation. However, more complex patterns of potential negative biases were evident, depending on the size and intensity of modeled rain cells.

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TRMM Radar Observations of Shallow Precipitation over the Tropical Oceans

Cited by 164 publications

References 69 publications

Implications of Warm Rain in Shallow Cumulus and Congestus Clouds for Large-Scale Circulations

Implications of Warm Rain in Shallow Cumulus and Congestus Clouds for Large-Scale Circulations

A 9-season TRMM Observation of the Austral Summer MJO and Low-frequency Equatorial Waves

An Interpretation of TRMM Radar Observations of Shallow Convection with a Rain Cell Model

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