Error Analysis and Modeling of GPM Dual-Frequency Precipitation Radar Near-surface Rainfall Product

2021 ◽  
Keyword(s):  
Standard Deviation ◽  
Systematic Error ◽  
Random Error ◽  
Convective Precipitation ◽  
Dual Frequency ◽  
Precipitation Radar ◽  
Near Surface ◽  
Surface Rainfall ◽  
Comparison Results ◽  
Stratiform Precipitation

Abstract The error characterization of rainfall products of spaceborne radar is essential for better applications of radar data, such as multi-source precipitation data fusion and hydrological modeling. In this study, we analyzed the error of the near-surface rainfall product of the dual-frequency precipitation radar (DPR) on the Global Precipitation Measurement Mission (GPM) and modeled it based on ground C-band dual-polarization radar (CDP) data with optimization rainfall retrieval. The comparison results show that the near-surface rainfall data were overestimated by light rain and slightly underestimated by heavy rain. The error of near-surface rainfall of the DPR was modeled as an additive model according to the comparison results. The systematic error of near-surface rainfall was in the form of a quadratic polynomial, while the systematic error of stratiform precipitation was smaller than that of convective precipitation. The random error was modeled as a Gaussian distribution centered at −1−0 mm h−1. The standard deviation of the Gaussian distribution of convective precipitation was 1.71 mm h−1 and the standard deviation of stratiform precipitation was 1.18 mm h−1, which is smaller than that of convective precipitation. In view of the precipitation retrieval algorithm of DPR, the error causes were analyzed from the reflectivity factor (Z) and the drop size distribution (DSD) parameters (Dm, Nw). The high accuracy of the reflectivity factor measurement results in a small systematic error. Importantly, the negative bias of Nw was very obvious when the rain type was convective precipitation, resulting in a large random error.

Collaborative Study of Modified Elmore Method for Mercury in Formulations

1971 ◽  
Vol 54 (3) ◽  
pp. 685-687
Author(s):  
James E Launer
Keyword(s):  
Standard Deviation ◽  
Systematic Error ◽  
Random Error ◽  
Collaborative Study ◽  
Test Pair ◽  
Titrimetric Method ◽  
Mercuric Nitrate ◽  
Thiocyanate Solution ◽  
Diluted Solution ◽  
Bearing Materials

Abstract The titrimetric method for mercury described by Elmore in 1946 was modified and collaboratively studied with formulations containing 6.7% phenylmercury urea in one test pair and 1% mercuric nitrate in another test pair. Mercury is determined in diluted solution, following reflux at 30 drops/min with fuming H2SO4-red fuming HNO3, by titration with standard thiocyanate solution, using ferric alum as indicator. The method is not applicable in presence of large quantities of chlorine-bearing materials. Single determinations on 4 samples by 14 collaborators showed that the standard deviation estimation of random error was 0.058 for phenylmercury urea and 0.004 for mercuric nitrate. Standard deviation estimates of systematic error were 0.048 and 0.009, respectively. The method has been adopted as official first action.

Genesis of Pre–Hurricane Felix (2007). Part II: Warm Core Formation, Precipitation Evolution, and Predictability

2010 ◽  
Vol 67 (6) ◽  
pp. 1730-1744 ◽  
Author(s):  
Zhuo Wang ◽  
M. T. Montgomery ◽  
T. J. Dunkerton
Keyword(s):  
Initial Conditions ◽  
Numerical Technique ◽  
Transformation Process ◽  
Tropical Storm ◽  
Convective Precipitation ◽  
Moist Convection ◽  
Near Surface ◽  
Warm Core ◽  
Stratiform Precipitation ◽  
Deep Moist Convection

Abstract This is the second of a two-part study examining the simulated formation of Atlantic Hurricane Felix (2007) in a cloud-representing framework. Here several open issues are addressed concerning the formation of the storm’s warm core, the evolution and respective contribution of stratiform versus convective precipitation within the parent wave’s pouch, and the sensitivity of the development pathway reported in Part I to different model physics options and initial conditions. All but one of the experiments include ice microphysics as represented by one of several parameterizations, and the partition of convective versus stratiform precipitation is accomplished using a standard numerical technique based on the high-resolution control experiment. The transition to a warm-core tropical cyclone from an initially cold-core, lower tropospheric wave disturbance is analyzed first. As part of this transformation process, it is shown that deep moist convection is sustained near the pouch center. Both convective and stratiform precipitation rates increase with time. While stratiform precipitation occupies a larger area even at the tropical storm stage, deep moist convection makes a comparable contribution to the total rain rate at the pregenesis stage, and a larger contribution than stratiform processes at the storm stage. The convergence profile averaged near the pouch center is found to become dominantly convective with increasing deep moist convective activity there. Low-level convergence forced by interior diabatic heating plays a key role in forming and intensifying the near-surface closed circulation, while the midlevel convergence associated with stratiform precipitation helps to increase the midlevel circulation and thereby contributes to the formation and upward extension of a tropospheric-deep cyclonic vortex. Sensitivity tests with different model physics options and initial conditions demonstrate a similar pregenesis evolution. These tests suggest that the genesis location of a tropical storm is largely controlled by the parent wave’s critical layer, whereas the genesis time and intensity of the protovortex depend on the details of the mesoscale organization, which is less predictable. Some implications of the findings are discussed.

scholarly journals Adapting Passive Microwave-Based Precipitation Algorithms to Variable Microwave Land Surface Emissivity to Improve Precipitation Estimation from the GPM Constellation

2021 ◽  
Author(s):  
F. Joseph Turk ◽  
Sarah E. Ringerud ◽  
Yalei You ◽  
Andrea Camplani ◽  
Daniele Casella ◽  
...  
Keyword(s):  
Land Surface ◽  
Climate Models ◽  
Passive Microwave ◽  
Earth Surface ◽  
Surface Emissivity ◽  
Dual Frequency ◽  
Precipitation Radar ◽  
Near Surface ◽  
Surface Precipitation ◽  
Precipitation Measurement

AbstractA fully global satellite-based precipitation estimate that can transition across changing Earth surface and complex land/water conditions is an important capability for many hydrological applications, and for independent evaluation of the precipitation derived from weather and climate models. This capability is inherently challenging owing to the complexity of the surface geophysical properties upon which the satellite-based instruments view. To date, these satellite observations originate primarily from a variety of wide-swath passive microwave (MW) imagers and sounders. In contrast to open ocean and large water bodies, the surface emissivity contribution to passive MW measurements is much more variable for land surfaces, with varying sensitivities to near-surface precipitation. The NASA/JAXA Global Precipitation Measurement (GPM) spacecraft (2014-current) is equipped with a dual-frequency precipitation radar and a multichannel passive MW imaging radiometer specifically designed for precipitation measurement, covering substantially more land area than its predecessor Tropical Rainfall Measuring Mission (TRMM). The synergy between GPM’s instruments has guided a number of new frameworks for passive MW precipitation retrieval algorithms, whereby the information carried by the single narrow-swath precipitation radar is exploited to recover precipitation from a disparate constellation of passive MW imagers and sounders. With over six years of increased land surface coverage provided by GPM, new insight has been gained into the nature of the microwave surface emissivity over land and ice/snow covered surfaces, leading to improvements in a number of physical and semi-physical based precipitation retrieval techniques that adapt to variable Earth surface conditions. In this manuscript, the workings and capabilities of several of these approaches are highlighted.

Improvements in Detection of Light Precipitation with the Global Precipitation Measurement Dual-Frequency Precipitation Radar (GPM DPR)

2016 ◽  
Vol 33 (4) ◽  
pp. 653-667 ◽  
Author(s):  
Atsushi Hamada ◽  
Yukari N. Takayabu
Keyword(s):  
Deep Convection ◽  
Convective Precipitation ◽  
Dual Frequency ◽  
Precipitation Radar ◽  
Precipitation Measurement ◽  
Subtropical Oceans ◽  
Global Precipitation Measurement ◽  
Global Precipitation ◽  
The Impact ◽  
Light Precipitation

AbstractThis paper demonstrates the impact of the enhancement in detectability by the dual-frequency precipitation radar (DPR) on board the Global Precipitation Measurement (GPM) core observatory. By setting two minimum detectable reflectivities—12 and 18 dBZ—artificially to 6 months of GPM DPR measurements, the precipitation occurrence and volume increase by ~21.1% and ~1.9%, respectively, between 40°S and 40°N.GPM DPR is found to be able to detect light precipitation, which mainly consists of two distinct types. One type is shallow precipitation, which is most significant for convective precipitation over eastern parts of subtropical oceans, where deep convection is typically suppressed. The other type is probably associated with lower parts of anvil clouds associated with organized precipitation systems.While these echoes have lower reflectivities than the official value of the minimum detectable reflectivity, they are found to mostly consist of true precipitation signals, suggesting that the official value may be too conservative for some sort of meteorological analyses. These results are expected to further the understanding of both global energy and water budgets and the diabatic heating distribution.

scholarly journals Differences between the Surface Precipitation Estimates from the TRMM Precipitation Radar and Passive Microwave Radiometer Version 7 Products

2014 ◽  
Vol 15 (6) ◽  
pp. 2157-2175 ◽  
Author(s):  
Chuntao Liu ◽  
Edward Zipser
Keyword(s):  
Large Scale ◽  
Microwave Radiometer ◽  
North Indian Ocean ◽  
Passive Microwave ◽  
Convective Precipitation ◽  
Trade Wind ◽  
Precipitation Radar ◽  
Near Surface ◽  
Surface Precipitation ◽  
East Pacific

Abstract With 15 yr of the Tropical Rainfall Measuring Mission (TRMM) observations, the passive microwave radiometers [TRMM Microwave Imager (TMI)] and the precipitation radar (PR) report a close geographical distribution of annual precipitation between 36°S and 36°N. However, large discrepancies between PR and TMI precipitation retrievals are also found over several specific regions, such as central Africa, the Amazon, the tropical east Pacific, and north Indian Ocean. To understand these discrepancies, the PR near-surface and the TMI surface precipitation retrievals are compared at both pixel and precipitation system levels using collocated pixels and a precipitation feature database from 1998 to 2012. Over land, the TMI overestimates precipitation in deep and intense convective systems, but misses significant amounts of warm rainfall in shallow systems. Over the ocean, because of the partial beam filling of large footprints of the lower-frequency sensors, the TMI reports a larger precipitation area than the PR and underestimates the precipitation rate in the convective precipitation region. The TMI tends to overestimate precipitation compared to the PR in a large proportion of shallow systems over the tropical east Pacific and trade wind regions with large-scale descent. The PR tends to overestimate precipitation compared to the TMI in a large proportion of shallow systems over rainy oceans, such as the west Pacific and the Atlantic ITCZ. All these findings imply that there are still large uncertainties in the precipitation climatology over some regions. Further ground validation campaigns are still needed, especially over the ocean.

scholarly journals Characteristics of Monsoon Rainfall around the Himalayas Revealed by TRMM Precipitation Radar

2005 ◽  
Vol 133 (1) ◽  
pp. 149-165 ◽  
Author(s):  
B. C. Bhatt ◽  
K. Nakamura
Keyword(s):  
Tibetan Plateau ◽  
Diurnal Cycle ◽  
Rain Rate ◽  
Spatial And Temporal Variability ◽  
The Tibetan Plateau ◽  
The South ◽  
Precipitation Radar ◽  
Near Surface ◽  
Light Rain ◽  
Surface Rainfall

Abstract The climatological features of the diurnal cycle and its spatial and temporal variability are investigated around the Himalayas using hourly, 0.05° × 0.05° grid, near-surface rainfall data from the Precipitation Radar (PR) aboard the Tropical Rainfall Measuring Mission (TRMM) satellite during June–July–August (JJA) of 1998–2002. Though sampling errors inherent to TRMM PR measurements around the Himalayas could influence results, PR-observed precipitation features show agreement with previous studies in this region. The analysis of precipitation characteristics presented here is based on two rain-rate thresholds: (a) light rain rate (≤5 mm h−1), and (b) moderate to heavy rain rate (>5 mm h−1). The results suggest that afternoon to evening precipitation is noticed as embedded convection within a large region of light rain over the south-facing slopes of the Himalayas. The moderate to heavy conditional rain rate exhibits a relatively stronger diurnal cycle of precipitation in this region. However, this may be biased because of sampling. Almost all the Tibetan Plateau shows light rain activity. The Tibetan Plateau and northern Indian subcontinent regions are characterized by daytime maximum precipitation. From the analysis of near-surface rainfall over the finescale topography, it is observed that daytime (1200–1800 LT) precipitation is concentrated over the ridges and strong ridge–valley gradients with rain appearing over the south-facing slopes of the Himalayas. During midnight–early morning, intense rainfall concentrates over the ridges as well as in river valleys. Precipitation broadening and movement are noticed during this time period.

scholarly journals Linkage among Ice Crystal Microphysics, Mesoscale Dynamics and Cloud and Precipitation Structures Revealed by Collocated Microwave Radiometer and Multi-frequency Radar Observations

2020 ◽  
Author(s):  
Jie Gong ◽  
Xiping Zeng ◽  
Dong L. Wu ◽  
S. Joseph Munchak ◽  
Xiaowen Li ◽  
...  
Keyword(s):  
Deep Convection ◽  
Life Stage ◽  
Microwave Radiometer ◽  
Onset Time ◽  
Radiation Budget ◽  
Convective Precipitation ◽  
Squall Line ◽  
Dual Frequency ◽  
Surface Precipitation ◽  
Stratiform Precipitation

Abstract. Ice clouds and falling snow are ubiquitous globally and play important roles in the Earth's radiation budget and precipitation processes. Ice particle microphysical properties (e.g., size, habit and orientation) are not only influenced by ambient environment's dynamic and thermodynamic conditions, but also intimately connect to the cloud radiative effects and particle fall speeds, which therefore impact up to the future climate projection and down to the details of the surface precipitation (e.g., onset-time, location, type and strength). Our previous work revealed that high-frequency Polarimetric radiance Difference (PD) from passive microwave sensors is a good indicator of the bulk aspect ratio of horizontally oriented ice particles that are often occur inside anvil clouds and/or stratiform precipitations. In this current work, we further investigate the dynamic/thermodynamic mechanisms and cloud/precipitation structures associated with ice-phase microphysics corresponding to different PD signals. In order to do so, collocated CloudSat radar (W-band) and Global Precipitation Measurement Dual-frequency Precipitation Radar (GPM-DPR, Ku/Ka bands) observations as well as European Centre for Medium-Range Weather Forecasts (ECMWF) atmosphere background profiles are grouped according to the magnitude of PD for only stratiform precipitation and/or anvil cloud scenes. We found that horizontally-oriented snow aggregates or large snow particles are likely the major contributor to the high-PD signals at 166 GHz, while low-PD magnitudes can be attributed to small cloud ice, randomly oriented snow aggregates, riming snow or super-cooled water. Further, high (low) PD scenes are found to be associated with stronger (weaker) wind shear and higher (lower) ambient humidity, both of which help promote (prohibit) the growth of frozen particles and the organization of convective systems. An ensemble of squall line cases is studied at the end to demonstrate that the PD asymmetry in the leading and trailing edges of the deep convection line is closely tied to the anvil cloud and stratiform precipitation layers respectively, suggesting the potential usefulness of PD as a proxy of stratiform/convective precipitation flag, as well as a proxy of convection life stage.

scholarly journals Linkage among ice crystal microphysics, mesoscale dynamics, and cloud and precipitation structures revealed by collocated microwave radiometer and multifrequency radar observations

2020 ◽  
Vol 20 (21) ◽  
pp. 12633-12653
Author(s):  
Jie Gong ◽  
Xiping Zeng ◽  
Dong L. Wu ◽  
S. Joseph Munchak ◽  
Xiaowen Li ◽  
...  
Keyword(s):  
Deep Convection ◽  
Life Stage ◽  
Microwave Radiometer ◽  
Onset Time ◽  
Radiation Budget ◽  
Convective Precipitation ◽  
Squall Line ◽  
Dual Frequency ◽  
Surface Precipitation ◽  
Stratiform Precipitation

Abstract. Ice clouds and falling snow are ubiquitous globally and play important roles in the Earth's radiation budget and precipitation processes. Ice particle microphysical properties (e.g., size, habit and orientation) are not only influenced by the ambient environment's dynamic and thermodynamic conditions, but are also intimately connected to the cloud radiative effects and particle fall speeds, which therefore have an impact on future climate projection as well as on the details of the surface precipitation (e.g., onset time, location, type and strength). Our previous work revealed that high-frequency (> 150 GHz) polarimetric radiance difference (PD) from passive microwave sensors is a good indicator of the bulk aspect ratio of horizontally oriented ice particles that often occur inside anvil clouds and/or stratiform precipitation. In this current work, we further investigate the dynamic and thermodynamic mechanisms and cloud–precipitation structures associated with ice-phase microphysics corresponding to different PD signals. In order to do so, collocated CloudSat radar (W-band) and Global Precipitation Measurement Dual-frequency Precipitation Radar (GPM DPR, Ku–Ka-bands) observations as well as European Centre for Medium-Range Weather Forecasts (ECMWF) atmosphere background profiles are grouped according to the magnitude of PD for only stratiform precipitation and/or anvil cloud scenes. We found that horizontally oriented snow aggregates or large snow particles are likely the major contributor to the high-PD signals at 166 GHz, while low-PD magnitudes can be attributed to small cloud ice, randomly oriented snow aggregates, riming snow or supercooled water. Further, high-PD (low-PD) scenes are found to be associated with stronger (weaker) wind shear and higher (lower) ambient humidity, both of which help promote (prohibit) the growth of frozen particles and the organization of convective systems. An ensemble of squall line cases is studied at the end to demonstrate that the PD asymmetry in the leading and trailing edges of the deep convection line is closely tied to the anvil cloud and stratiform precipitation layers, respectively, suggesting the potential usefulness of PD as a proxy of stratiform–convective precipitation flag, as well as a proxy of convection life stage.

Collaborative Study of a Colorimetric Method for Paraquat in Formulations

1968 ◽  
Vol 51 (6) ◽  
pp. 1306-1309
Author(s):  
A A Carlstrom
Keyword(s):  
Free Radical ◽  
Standard Deviation ◽  
Systematic Error ◽  
Random Error ◽  
Collaborative Study ◽  
Colorimetric Method ◽  
Sodium Dithionite ◽  
Reference Standard ◽  
Standard Curve ◽  
Diluted Solution

Abstract A colorimetric method described by Yuen, Bagness, and Myles in 1967 was collaboratively studied with paraquat formulations containing 2 lb/gal. (about 20% cation). Paraquat is determined in a diluted solution by measuring the absorbance, at 600 mμ, of the blue free radical produced by reduction with alkaline sodium dithionite, and its absorbance is compared to a reference standard curve. Standard deviation estimation of random error was 0.22 for paraquat dimethylsulfate formulations and 0.26 for paraquat dichloride. Standard deviation estimates of systematic error were 0.20 and 0.62, respectively. The method is recommended for adoption as official, first action.

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