Quantitative Cross Validation of Space-Based and Ground-Based Radar Observations

Bolen, S.; Chandrasekar, V.

doi:10.1175/1520-0450(2001)040<2071:qcvosb>2.0.co;2

Cited by 88 publications

(52 citation statements)

References 5 publications

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“…Low-level reflectivity measurements are also subject to attenuation due to the operating wavelength of the PR. Comparisons with non-attenuated ground radar observations suggest that the PR 2A25 algorithm does well at correcting for attenuation at altitudes near 2 km (Bolen and Chandrasekar 2000;Schumacher and Houze 2000). As in Schumacher and Houze (2003a), binned orbital 2 km reflectivity is converted to rain rate using the TRMM version 5 convective and stratiform near-surface initial reflectivity-rain rate (Z-R) relations (Z = 148 R 1.55 and Z = 276 R 1.49 , respectively).…”

Section: Tropics-wide Statistics Of Reflectivity Profilesmentioning

confidence: 99%

Stratiform precipitation production over sub‐Saharan Africa and the tropical East Atlantic as observed by TRMM

Schumacher

Houze

2006

Quart J Royal Meteoro Soc

114

111

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SUMMARYConvective systems over sub-Saharan Africa and the tropical East Atlantic have distinct geographical and seasonal variations in convective intensity and stratiform precipitation production as observed by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar. Over the East Atlantic, convective rain rates are lower and the percentage of total rain that is stratiform is higher compared to over West Africa. In addition, the East Atlantic has more shallow precipitating convection and less non-precipitating anvil than sub-Saharan Africa. During the monsoon season, convective rain rates and the percentage of area covered by anvil decrease while the stratiform rain fraction and number of shallow convective cells increase in both regions compared to the pre-monsoon season. These observations suggest that convective sustainability, i.e. the ability of a region to continually support convection, helps determine whether a robust stratiform rain area or non-precipitating anvil forms.In addition to convective sustainability, wind shear and the Saharan Air Layer appear to play important roles in the formation and extent of the stratiform components of convective cloud systems. Strong winds associated with the African Easterly Jet and dry intrusions from the Sahara Desert may increase sublimation and evaporation at mid levels, resulting in less stratiform rain. Strong upper-level shear associated with the African Easterly Jet may further hinder stratiform rain production by displacing hydrometeors that form in the convective cells beyond the area of mesoscale rain formation. When the upper-level Tropical Easterly Jet strengthens during the monsoon season, upper-level shear is reduced dramatically and stratiform rain areas form in preference to non-raining anvil.

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Section: Tropics-wide Statistics Of Reflectivity Profilesmentioning

confidence: 99%

Stratiform precipitation production over sub‐Saharan Africa and the tropical East Atlantic as observed by TRMM

Schumacher

Houze

2006

Quart J Royal Meteoro Soc

114

111

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“…During and subsequent to the project, several independent estimates of the S-band radar reflectivity calibration offset were made utilizing engineering measurements of the radar hardware (G. Mueller 2000, personal communication), comparison with version-4 TRMM PR data (Bolen and Chandrasekar 2000), and comparison with rain gauge data (C. Schumacher 2000, personal communication). The consensus calibration correction with uncertainty from these estimates is 5 dB Ϯ 2 dB (details may be found online at www.atmos.…”

Section: S-band and C-band Radar Scan Strategies And Calibration For mentioning

confidence: 99%

Physical Characterization of Tropical Oceanic Convection Observed in KWAJEX

Yuter

Houze

Smith

et al. 2005

Journal of Applied Meteorology

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The Tropical Rainfall Measuring Mission (TRMM) Kwajalein Experiment (KWAJEX) was designed to obtain an empirical physical characterization of precipitating convective clouds over the tropical ocean. Coordinated datasets were collected by three aircraft, one ship, five upper-air sounding sites, and a variety of continuously recording remote and in situ surface-based sensors, including scanning Doppler radars, profilers, disdrometers, and rain gauges. This paper describes the physical characterization of the Kwajalein cloud population that has emerged from analyses of datasets that were obtained during KWAJEX and combined with long-term TRMM ground validation site observations encompassing three rainy seasons. The spatial and temporal dimensions of the precipitation entities exhibit a lognormal probability distribution, as has been observed over other parts of the tropical ocean. The diurnal cycle of the convection is also generally similar to that seen over other tropical oceans. The largest precipitating cloud elements-those with rain areas exceeding 14 000 km 2 -have the most pronounced diurnal cycle, with a maximum frequency of occurrence before dawn; the smallest rain areas are most frequent in the afternoon. The large systems exhibited stratiform rain areas juxtaposed with convective regions. Frequency distributions of dual-Doppler radar data showed narrow versus broad spectra of divergence in the stratiform and convective regions, respectively, as expected because strong up-and downdrafts are absent in the stratiform regions. The dual-Doppler profiles consistently showed low-level convergence and upper-level divergence in convective regions and midlevel convergence sandwiched between lower-and upper-level divergence in stratiform regions. However, the magnitudes of divergence are sensitive to assumptions made in classifying the radar echoes as convective or stratiform. This sensitivity implies that heating profiles derived from satellite radar data will be sensitive to the details of the scheme used to separate convective and stratiform rain areas. Comparison of airborne passive microwave data with ground-based radar data indicates that the pattern of scattering of 85-GHz radiance by ice particles in the upper portions of KWAJEX precipitating clouds is poorly correlated with the precipitation pattern at lower levels while the emission channels (10 and 19 GHz) have brightness temperature patterns that closely correspond to the lower-level precipitation structure. In situ ice particle imagery obtained by aircraft at upper levels (ϳ11 km) shows that the concentrations of ice particles of all densities are greater in the upper portions of active convective rain regions and lower in the upper portions of stratiform regions, probably because the active updrafts convey the particles to upper levels, whereas in the stratiform regions sedimentation removes the larger ice particles over time. Low-level aircraft flying in the rain layer show similar total drop concentrations in and out of convective cells, but...

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“…In addition to the attenuation correction, accurate radar calibration is the key to ensure reliable estimates of hydrometeor parameters. Although a variety of approaches can be used to address this issue, such as the internal calibration from which satellite instrument data have been used to assess the stability of the transmitter and receiver (Kawanishi et al 2000), the most important type of external calibration is perhaps the comparisons of the PR-derived radar reflectivities with the estimates of the same quantities made with well-calibrated ground-based radars (Anagnostou et al 2001;Schumacher and Houze 2000;Bolen and Chandrasekar 2000;Liao et al 2001). Near the top of stratiform storms where dry snow is almost exclusively present, the TRMM PR returns are nearly attenuation free.…”

Section: Introductionmentioning

confidence: 99%

Validation of TRMM Precipitation Radar through Comparison of Its Multiyear Measurements with Ground-Based Radar

Liao

Meneghini

2009

Journal of Applied Meteorology and Climatology

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A procedure to accurately resample spaceborne and ground-based radar data is described, and then applied to the measurements taken from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and the ground-based Weather Surveillance Radar-1988 Doppler (WSR-88D or WSR) for the validation of the PR measurements and estimates. Through comparisons with the well-calibrated, non-attenuated WSR at Melbourne, Florida for the period 1998-2007, the calibration of the Precipitation Radar (PR) aboard the TRMM satellite is checked using measurements near the storm top. Analysis of the results indicates that the PR, after taking into account differences in radar reflectivity factors between the PR and WSR, has a small positive bias of 0.8 dB relative to the WSR, implying a soundness of the PR calibration in view of the uncertainties involved in the comparisons. Comparisons between the PR and WSR reflectivities are also made near the surface for evaluation of the attenuation-correction procedures used in the PR algorithms. It is found that the PR attenuation is accurately corrected in stratiform rain but is underestimated in convective rain, particularly in heavy rain. Tests of the PR estimates of rainfall rate are conducted through comparisons in the overlap area between the TRMM overpass and WSR scan. Analyses of the data are made both on a conditional basis, in which the instantaneous rain rates are compared only at those pixels where both the PR and WSR detect rain, and an unconditional basis, in which the area-averaged rain rates are estimated independently for the PR and WSR. Results of the conditional rain comparisons show that the PR-derived rain is about 9% greater and 19% less than the WSR estimates for stratiform and convective storms, respectively. Overall, the PR tends to underestimate the conditional mean rain rate by 8% for all rain categories, a finding that conforms to the results of the area-averaged rain (unconditional) comparisons.

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Quantitative Cross Validation of Space-Based and Ground-Based Radar Observations

Cited by 88 publications

References 5 publications

Stratiform precipitation production over sub‐Saharan Africa and the tropical East Atlantic as observed by TRMM

Stratiform precipitation production over sub‐Saharan Africa and the tropical East Atlantic as observed by TRMM

Physical Characterization of Tropical Oceanic Convection Observed in KWAJEX

Validation of TRMM Precipitation Radar through Comparison of Its Multiyear Measurements with Ground-Based Radar

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