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Brightband
Identification Based on Vertical Profiles of Reflectivity from the WSR-88D Jian Zhang, Carrie Langston, Kenneth Howard Journal of Atmospheric and Oceanic Technology Volume 25, Issue 10 (October 2008) pp. 1859-1872 doi: 10.1175/2008JTECHA1039.1 [Abstract]
[Full
Text] [PDF (2092 KB)] [Add
to Favorites] 0℃高度の同定は航空にとっても重要。 BBの自動判定法を開発した。BBの自動判定法の詳細とWSR-88Dでの結果との比較を示す。12/2’11 |
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The New French Operational Radar Rainfall
Product. Part I: Methodology P. Tabary Centre de Météorologie Radar, Direction des Systèmes
d’Observation, Météo-France,
Trappes, France Weather and Forecasting Volume 22, Issue 3 (June 2007) pp. 393-408 doi: 10.1175/WAF1004.1Abstract [Abstract]
[Full
Text] [PDF (1191 KB)] [Add
to Favorites] The New French
Operational Radar Rainfall Product. Part 1: Methodology Tabary 2007 Abstract A new radar-based
rainfall product has been developed at Météo-France
and is currently being deployed within the French operational Application
Radar à la Météorologie Infra-Synoptique
(ARAMIS) radar network. The rainfall product is based entirely on radar data
and comprises the following successive processing steps: 1) dynamic
identification of ground clutter based on the pulse-to-pulse fluctuation of
the radar signal, 2) reflectivity-to-rain-rate conversion using the
Marshall–Palmer Z–R relationship, 3) correction for partial beam blocking
using numerical simulations of the interaction between the radar wave and the
terrain, 4) correction for vertical profile of reflectivity (VPR) effects
based on ratio curves and a priori climatology-based VPR candidates, 5)
correction for nonsimultaneity of radar
measurements by making use of a cross-correlation advection field, 6)
weighted linear combination of the corrected reflectivity measurements
gathered at the various elevation angles of the volume coverage pattern, and
7) production of a 5-min rain accumulation using the advection field to
mitigate undersampling effects. In addition to the
final Cartesian, 512 km × 512 km, 1 km2 in resolution, radar rainfall
product, a map of quality indexes is automatically generated that allows for
assessing empirically the accuracy of the estimation. This new product has
been validated using 27 episodes observed during the autumns of 2002 and 2003
and the winter of 2005 by three S-band radars of the network. This paper is
entirely devoted to the description of the methodology. 【新規更新したフランスのレーダの紹介。要旨を見る限り偏波の特徴が記述されていない。6機が偏波らしい。図1】11/28’11 |
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The New French Operational Radar Rainfall
Product. Part II: Validation P. Tabary, J. Desplats, K. Do Khac, F. Eideliman, C. Gueguen, J-C.
Heinrich Centre de Météorologie Radar, Direction des Systèmes
d’Observation, Météo-France,
Trappes, France Weather and Forecasting Volume 22, Issue 3 (June 2007) pp. 409-427 doi: 10.1175/WAF1005.1Abstract [Abstract]
[Full
Text] [PDF (5055 KB)] [Add
to Favorites] The New French Operational
Radar Rainfall Product. Part II: Validation P. Tabary, et al 2007 Abstract A new operational
radar-based rainfall product has been developed at Météo-France
and is currently being deployed within the French operational network. The
new quantitative precipitation estimation (QPE) product is based entirely on
radar data and includes a series of modules aimed at correcting for ground
clutter, partial beam blocking, and vertical profile of reflectivity (VPR)
effects, as well as the nonsimultaneity of radar
measurements. The surface rainfall estimation is computed as a weighted mean
of the corrected tilts. In addition to the final QPE, a map of quality
indexes is systematically generated. This paper is devoted to the validation
of the new radar QPE. The VPR identification module has been specifically
validated by analyzing 489 precipitation events observed over 1 yr by a representative eight-radar subset of the network.
The conceptual model of VPR used in the QPE processing chain is shown to be
relevant. A climatology of the three shape parameters of the conceptual VPR (brightband peak, brightband
thickness, and upper-level decreasing rate) is established and the
radar-derived freezing-level heights are shown to be in good agreement with radiosonde data. A total of 27 precipitation events
observed by three S-band radars of the network during the winter of 2005 and
the autumns of 2002 and 2003 are used to compare the new radar QPE to the old
one. Results are stratified according to the distance to the radar and
according to the height of the freezing level. The Nash criterion is
increased from 0.23 to 0.62 at close range (below 50 km) and from 0.35 to
0.42 at long range (between 100 and 150 km). The relevance of the proposed
quality indexes is assessed by examining their statistical relationship with
long-term radar–rain gauge statistics. Mosaics of QPE and quality indexes are
also illustrated. VPRの概念モデルとして、BBの極大値、BBの厚さ、雪の層の増加率を利用した。11/28’11 |
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Real-Time Comparisons of VPR-Corrected
Daily Rainfall Estimates with a Gauge Mesonet Aldo Bellon, Gyu Won Lee, Alamelu Kilambi, Isztar Zawadzki Journal of Applied Meteorology and Climatology Volume 46, Issue 6 (June 2007) pp. 726-741 doi: 10.1175/JAM2502.1Abstract [Abstract]
[Full
Text] [PDF (1641 KB)] [Add
to Favorites] タイトル：メソネットで評価し、VPRで補正した日降水量の、オンライン評価 VPRの補正法の比較。C１：選択したデータセットの日積算雨量で補正。C２：オンライン雨量で補正。C1は全1時間の値を用いて参照するデータセット（1．5㎞）を決める。12/2’111 |
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A Polarimetric Radar Approach to Identify
Rain, Melting-Layer, and Snow Regions for Applying Corrections to Vertical
Profiles of Reflectivity Sergey Y. Matrosov, Kurt A.
Clark, David E. Kingsmill Journal of Applied Meteorology and Climatology Volume 46, Issue 2 (February 2007) pp. 154-166 doi: 10.1175/JAM2508.1 http://hydro.iis.u-tokyo.ac.jp/~koshida/review/0804.htm - Matrosov |
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Error Statistics of VPR Corrections in Stratiform Precipitation Aldo Bellon, Gyu Won Lee, Isztar Zawadzki Journal of Applied Meteorology Errors in surface rainfall estimates that are caused by
ignoring the vertical profile of reflectivity (VPR) and range effects have
been assessed by simulating how fine-resolution 3D reflectivity measurements
at close ranges are sampled by the radar at various ranges and heights.
Uncorrected and corrected accumulations from 33 events of mainly stratiform precipitation, with a recognizable melting
layer for over 250 h, have been generated using two basic procedures: (a) the
“near range” or “inner” VPR and (b) the intensity-dependent “climatological”
VPR. The root-mean-square (rms) error structure has
been derived as a function of height and range, for accumulations ranging
from 5 min to 2 h, for various brightband heights
and verification areas. However, it is the errors along the lowest default
height that are most relevant. The stratification of the results by the
height of the bright band is essential to understand the influence of the
bright band with range. The largest errors (>100% at near ranges without
correction) are encountered with lower and stronger bright bands. After
correction, errors of less than 20% can be achieved with method “a” but only
over large verification areas (>100 km2), with long accumulation intervals
(>45 minutes.), with bright bands that are relatively high (>2.5 km),
and for ranges within 130 km. The climatological correction yields errors
that are roughly 2 times as large. The results with the inner VPR method can
only be obtained by assuming conditions of spatial homogeneity in the VPR
structure of the rainfall fields. Simulations of the VPR variability have
indicated that larger errors are to be expected in real-time operations,
particularly when measurements are made inside the bright band. The magnitude
of these errors may approach those of a “realistic climatological” correction
that incorporates some uncertainty in the brightband
height. Volume 44, Issue 7 (July 2005) pp. 998-1015 doi: 10.1175/JAM2253.1Abstract [Abstract]
[Full
Text] [PDF (2127 KB)] [Add
to Favorites] VPRを入れた場合と入れない場合の雨量観測精度の比較。VPRはa)レーダ近傍のデータにより作成b)強度に依存した気候値の2通り用いた。 層状性降雨のブライトバンド高度を検証に用いた。もっとも大きなエラーが出現したのは低く強いブライトバンドであった。補正を行うとエラーは20%減少したが、算出方法a)の場合で、第領域100㎞2、長時間の積分(45分以上)、高度が高い(2.5㎞)、レーダからの距離が130㎞の場合だけであった。 【検証に用いた物理量は？】12/6’11 |
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Influence of the Vertical Profile of
Reflectivity on Radar-Estimated Rain Rates at Short Time Steps Alexis Berne, Guy Delrieu, Herve Andrieu, Jean-Dominique Creutin Journal of Hydrometeorology Volume 5, Issue 2 (April 2004) pp. 296-310 doi: 10.1175/1525-7541(2004)005<0296:IOTVPO>2.0.CO;2Abstract [Abstract]
[Full
Text] [PDF (1553 KB)] [Add
to Favorites] 鉛直方向に不均質があった場合にレーダ雨量にどのような影響があるかを、X帯のVレーダと、現業のS帯、雨量計25基つかって調べた。 VPRで補正した降水量と、補正しない降水量を、時間間隔を6分から30分の間で変化させて、評価した。強い地中海降水【有名なのか？】の12時間を含めても、VPRの効果は明瞭であった。Nash値は6分で0.85、30分で0.93、補正しないと0.15のままであった【値がへん？低すぎ？】。1点で空間分布を補正する件については、20㎞2(200㎞2)位が6分(30分)に有効であった。12/7’11 |
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Hydrologic Visibility of Weather Radar
Systems Operating in Mountainous Regions: Case Study for the Ardèche
Catchment (France) Thierry Pellarin, Guy Delrieu, Georges-Marie Saulnier,
Hervé Andrieu, Bertrand Vignal, Jean-Dominique Creutin Journal of Hydrometeorology Volume 3, Issue 5 (October 2002) pp. 539-555 A simulation procedure has been developed for use in predetermining
the expected quality of rain-rate estimates that a given weather radar system
operating in a mountainous region may obtain over a given hydrologic
catchment. This first application of what is referred to as the “hydrologic
visibility” concept focuses on the quantification of the rain-rate error
resulting from the effects of ground clutter, beam blockage, and the vertical
profile of reflectivity (VPR). The assessment of the impact of the space–time
structure of the radar error in terms of discharge at the catchment outlet is
also investigated using a distributed hydrologic model. A case study is presented for the Ardèche
catchment in France using the parameters of two S-band weather radars
operated by Météo-France at Nîmes
and Bollène. Radar rain-rate error generation and
rainfall–runoff simulations are performed using VPR and areal rainfall time
series representative of the Cévennes rain
climatology. The major impact of ground clutter on both rainfall and runoff
estimates is confirmed. The “hydrologic compositing procedure,” based on the
selection of the elevation angle minimizing the rain-rate error at a given
point, is shown to be preferable to the “pseudo-CAPPI” procedure based on
radar-range considerations only.
An almost perfect ground-clutter reduction (GCR) technique is
simulated in order to assess the effects of beam blockage and VPR alone.
These error sources lead to severe and slight rain underestimations for the Nîmes and Bollène radars,
respectively, over the Ardèche catchment. The results,
indicating an amplification of the errors on the discharge parameters (peak
discharge, runoff volume) compared to the areal rainfall error, are of
particular interest. They emphasize the need for refined corrections for
ground clutter, beam blockage, and VPR effects, in addition to the
optimization of the radar location and scanning strategy, if hydrologic
applications are foreseen. doi:
10.1175/1525-7541(2002)003<0539:HVOWRS>2.0.CO;2 目的：期待される降水量を事前に決定するときに用いるるときに使う再現手法を開発した【レーダ雨量を観測条件から推定する】。期待される降水量＝ 山地部で運用されているレーダが流域に関して観測するで、あろう値。クラッタ・遮蔽・VPRなどの影響があるときに、水文学的な見通し【雨がどれくらい降るか】を参照するために用いる。レーダデータのエラーがどの程度流出に影響を与えるかについて分布型モデルを用いて評価することもやっている。 事例解析は、フランスのアルデッシュ流域、2台のSバンドで観測している。レーダ雨量の誤差の発生と流出解析はVPRとスベンヌスの気候値を用いて実施した。クラッタがレーダ雨量と流出量に影響を与えていることが確認できる。エラーが最も小さくなるように複数仰角を用いて合成雨量を作成すると、レーダ雨量だけについていうと、疑似CAPPIを作るのに適している。12/8’11 |
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Large-Sample Evaluation of Two Methods to
Correct Range-Dependent Error for WSR-88D Rainfall Estimates Bertrand Vignal, Witold F. Krajewski Journal of Hydrometeorology Volume 2, Issue 5 (October 2001) pp. 490-504 The vertical variability of reflectivity is an
important source of error that affects estimations of rainfall quantity by
radar. This error can be reduced if the vertical profile of reflectivity
(VPR) is known. Different methods are available to determine VPR based on
volume-scan radar data. Two such methods were tested. The first, used in the
Swiss Meteorological Service, estimates a mean VPR directly from volumetric
radar data collected close to the radar. The second method takes into account
the spatial variability of reflectivity and relies on solving an inverse
problem in determination of the local profile. To test these methods, two
years of archived level-II radar data from the Weather Surveillance
Radar-1988 Doppler (WSR-88D) located in Tulsa, Oklahoma, and the
corresponding rain gauge observations from the Oklahoma Mesonet
were used. The results, obtained by comparing rain estimates from radar data
corrected for the VPR influence with rain gauge observations, show the
benefits of the methods—and also their limitations. The performance of the
two methods is similar, but the inverse method consistently provides better
results. However, for use in operational environments, it would require
substantially more computational resources than the first method. doi:
10.1175/1525-7541(2001)002<0490:LSEOTM>2.0.CO;2 VPRが降水観測に与える影響についてしらべた。スイスで実施されている技術をオクラホマのWSR88Dに応用。単純なボリューム観測からVPRを出す方法（スイスの方法）とレーダ反射因子の空間変動を加味して逆値問題として求める方法の2つを12/12’11 |
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Three Methods to Determine Profiles of
Reflectivity from Volumetric Radar Data to Correct Precipitation Estimates Bertrand Vignal, Gianmario Galli, Jürg Joss, Urs Germann Journal of Applied Meteorology Volume 39, Issue 10 (October 2000) pp. 1715-1726 The vertical variability of radar reflectivity reduces
the reliability of precipitation estimation by radar, especially in complex
orography. This important source of error can, at least partially, be
corrected for, if the vertical profile of radar reflectivity (VPR) is known.
This work addresses three ways to determine VPR from volumetric radar data
for correcting precipitation estimates. The first way uses a climatological
profile. The second method, operational in Switzerland, takes the actual
weather conditions into account: a mean profile is estimated directly from
volumetric radar data collected close to the radar. The third way determines
the identified profile, taking the variability of the VPRs in space into
account. This approach yields local estimates of the profile (on areas of
about 20 km × 20 km) based on an inverse method. Two cases, a convective
event and a stratiform event, are used to
illustrate the three ways for determining the VPR, and the resulting
improvement, verified with rain gauges. An enlarged dataset of nine cases
shows that a correction based on a climatological profile already improves
the accuracy of rain estimates by radar significantly: the fractional
standard error (FSE) is reduced from the noncorrected
44% to 31%. By correcting with a single, mean profile (averaged over 1 h
using real-time data), the FSE is further reduced from 31% to 25%. Last, the
use of 70 locally identified profiles leads to best results (FSE = 23%). A
higher improvement (lower FSE) is obtained for the stratiform
rain event than for the convective case. doi: 10.1175/1520-0450-39.10.1715 Zの鉛直方向の変動が 降雨推定に誤差を与えるので、VPRを知ることは補正に重要である。本研究ではVPR計算の3つの手法を提案する。1）気候値2）気象条件を加味してレーダ近傍での体積探査結果を利用3）VPRの空間変動を加味して分布を決定【前論文の手法】。3つ目の手法は20×20㎞の領域での逆値問題として求める。対流性、層状性の2降雨について精度評価を行った。気候値を用いた場合に改善が示されており部分標準誤差【？】で44%⇒31%となった。一つの平均分布を使うと３１％⇒25%、最後に最善案は23%となった。層状性の方が、補正が良く効いた。12/13’11 |
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Identification of Vertical Profiles of
Reflectivity from Volume Scan Radar Data Bertrand Vignal, Hervé Andrieu, J. Dominique Creutin Journal of Applied Meteorology Volume 38, Issue 8 (August 1999) pp. 1214-1228 The vertical variability of reflectivity in the radar
beam is an important source of error that interferes with a reliable
estimation of the rainfall rate by radar. This source of error can be
corrected if the vertical profile of reflectivity (VPR) has been previously
determined. This paper presents a method for determining local VPRs from
volume scan radar data, that is, from radar data recorded at multiple
elevation angles. It is shown that the VPR directly provided by volume scan
radar data differs from the true one, which can make it inappropriate to the
correction of radar data for the VPR influence. The VPR identification
method, based on the analysis of ratios of radar measurements at multiple
elevations angles, is then described. The application conditions of the
method are defined through sensitivity tests applied to a synthetic case. A
“real world” case study allows performing a first evaluation of the proposed
method. This analysis demonstrates that the identification of local VPRs and
the correction for their influence at a scale of about 100 km2 contributes to
improving the reliability of rainfall measurement by radar. Moreover, it is
shown that a correction of radar data based on identified VPRs performs
better than a correction based on the VPRs directly deduced from volume scan
radar data. This last point confirms the importance of the VPR identification
stage in the correction of radar data for this source of error. doi: 10.1175/1520-0450(1999)038<1214:IOVPOR>2.0.CO;2 VPRを計算するのに多仰角データから作成するのでなく、体積探査から求める方法を提案する。VPRを降水量推定に用いることで推定精度が高くなる。人工的な事例に当てはめる 感度テストを行い今回の手法の条件を検討した。100㎞2の流域に適用したときに改善が見られた。体積探査の結果が重要であるので、レーダのエラーはVPRを決める段階で除去しておく必要がある。12/14’11 |
12 ERAD 2010 Tabary フランスのCバンドレーダネットワークの説明
2.1 ZDRのための天頂観測
15分に1回、フランスにある10基の偏波レーダが天頂を観測する。
2.5ρhvの80%観測
SNが大きいところでρhvが0. 95より小さいときはエラーと考える。
3.3ブライトバンドの同定には観測されたρhvと計算のρhvの相関が高い場合にVPRを信用し、BBを決める。11/29’11