scholarly journals Supplementary material to "Consistency and representativeness of integrated water vapour from ground-based GPS observations and ERA-Interim reanalysis"

2019 ◽  
Author(s):  
Olivier Bock ◽  
Ana C. Parracho
Keyword(s):  
Water Vapour ◽  
Integrated Water Vapour ◽  
Supplementary Material ◽  
Gps Observations

scholarly journals Consistency and representativeness of integrated water vapour from ground-based GPS observations and ERA-Interim reanalysis

2019 ◽  
Vol 19 (14) ◽  
pp. 9453-9468 ◽  
Author(s):  
Olivier Bock ◽  
Ana C. Parracho
Keyword(s):  
Standard Deviation ◽  
Water Vapour ◽  
Spatiotemporal Variability ◽  
Small Scale ◽  
Comparison Results ◽  
Integrated Water Vapour ◽  
Grid Points ◽  
Error Statistic ◽  
Climatic Features ◽  
Gps Observations

Abstract. This study examines the consistency and representativeness differences of daily integrated water vapour (IWV) data from ERA-Interim reanalysis and GPS observations at 120 global sites over a 16-year period (1995–2010). Various comparison statistics are analysed as a function of geographic, topographic, and climatic features. A small (±1 kg m−2) bias is found in the reanalysis across latitudes (moist in northern and southern midlatitudes and dry in the tropics). The standard deviation of daily IWV differences is generally below 2 kg m−2 but peaks in the northern and southern storm-track regions. In general, the larger IWV differences are explained by increased representativeness errors, when GPS observations capture some small-scale variability that is not resolved by the reanalysis. A representativeness error statistic is proposed which measures the spatiotemporal variability in the vicinity of the GPS sites, based on reanalysis data at the four surrounding grid points. It allows to predict the standard deviation of daily IWV differences with a correlation of 0.73. In general, representativeness differences can be reduced by temporal averaging and spatial interpolation from the four surrounding grid points. A small number of outlying cases (15 sites) which do not follow the general tendencies are further examined. It is found that their special topographic and climatic features strongly enhance the representativeness errors (e.g. steep topography, coastlines, and strong seasonal cycle in monsoon regions). Discarding these sites significantly improves the global ERA-Interim and GPS comparison results. The selection of sites a priori, based on the representativeness error statistic, is able to detect 11 out of the 15 sites and improve the comparison results by 20 % to 30 %.

scholarly journals Global IWV trends and variability in atmospheric reanalyses and GPS observations

2018 ◽  
Author(s):  
Ana C. Parracho ◽  
Olivier Bock ◽  
Sophie Bastin
Keyword(s):  
Time Series ◽  
Water Vapour ◽  
Reanalysis Data ◽  
Northern Africa ◽  
Data Sets ◽  
Wind Fields ◽  
Mountain Ranges ◽  
Integrated Water Vapour ◽  
Good Agreement ◽  
Gps Observations

Abstract. Water vapour plays a key role in the climate system. However, its short residence time in the atmosphere and its high variability in space and time make it challenging when it comes to study trends and variability. There are several sources of water vapour data. In this work we use Integrated Water Vapour (IWV) estimated from GPS observations and atmospheric reanalyses. Monthly and seasonal means, interannual variability, and linear trends are analysed and compared for the period between 1995 and 2010. A general good agreement is found but this study highlights issues in both GPS and reanalysis data sets. In GPS, gaps and inhomogeneities in the time series are evidenced, which affect mainly variability and trend estimation. In ERA-Interim, too strong trends in certain regions (e.g. drying over northern Africa and Australia, and moistening over northern South America) were found. Representativeness differences in coastal areas and regions of complex topography (mountain ranges, islands) are also evidenced as limitations to the intercomparison of the point observations and reanalysis data. A general good agreement is found for the means and variabilities, with the exception of a few stations where representativeness issues are suspected. Monthly IWV trends are also found to be in good sign agreement, with the exception of a handful of stations where, in addition to representativeness errors, there might be inhomogeneities in the GPS time series. Seasonal trends are found to be different and more intense than monthly trends, which emphasizes the influence of atmospheric circulation on IWV trends. In order to assess strong trends over regions lacking GPS stations, a second reanalysis, MERRA-2, is introduced. The period of analysis is extended to 1980–2016 (the longest period the reanalyses have in common) and differences with the shorter period are found. This exemplifies how much IWV trends are dependent on the time period at study and must be interpreted carefully. Temperature trends are also computed for both reanalyses. The Clausius-Clapeyron scaling ratio is found to not be a good humidity proxy at seasonal and regional scales. Regions over northern Africa and Australia, where ERA-Interim and MERRA-2 disagree, are investigated further. Dynamics at these regions is assessed by analyzing the wind fields at 925 hPa and is shown to be tightly linked with the trends and variability in IWV.

scholarly journals WATER VAPOUR WEIGHTED MEAN TEMPERATURE MODEL FOR GPS-DERIVED INTEGRATED WATER VAPOUR IN PENINSULAR MALAYSIA

2017 ◽  
Vol XLII-4/W5 ◽  
pp. 127-135 ◽  
Author(s):  
T. A. Musa ◽  
M. H. Mazlan ◽  
Y. D. Opaluwa ◽  
I. A. Musliman ◽  
Z. M. Radzi
Keyword(s):  
Water Vapour ◽  
Diurnal Cycle ◽  
Specific Model ◽  
Regional Model ◽  
Peninsular Malaysia ◽  
Site Specific ◽  
Weighted Mean Temperature ◽  
Integrated Water Vapour ◽  
Relationship Of ◽  
The Impact

This paper presents the development of T<sub>M</sub> model by using the radiosonde stations from Peninsular Malaysia. Two types of T<sub>M</sub> model were developed; site-specific and regional models. The result revealed that the estimation from site-specific model has small improvement compared to the regional model, indicating that the regional model is adequately to use in estimation of GPS-derived IWV over Peninsular Malaysia. Meanwhile, this study found that the diurnal cycle of T<sub>S</sub> has influenced the T<sub>M</sub>&amp;ndash;T<sub>S</sub> relationship. The separation between daytime and nighttime observation can improve the relationship of T<sub>M</sub>&amp;ndash;T<sub>S</sub>. However, the impact of diurnal cycle to IWV estimation is less than 1&amp;thinsp;%. The T<sub>M</sub> model from Global and Tropic also been evaluated. The Tropic T<sub>M</sub> model is superior to be utilized as compared to the Global T<sub>M</sub> model.

scholarly journals Supplementary material to "The SPARC water vapour assessment II: Comparison of stratospheric and lower mesospheric water vapour time series observed from satellites"

2018 ◽  
Author(s):  
Farahnaz Khosrawi ◽  
Stefan Lossow ◽  
Gabriele P. Stiller ◽  
Karen H. Rosenlof ◽  
Joachim Urban ◽  
...  
Keyword(s):  
Time Series ◽  
Water Vapour ◽  
Supplementary Material

scholarly journals SPATIO-TEMPORAL ESTIMATION OF INTEGRATED WATER VAPOUR OVER THE MALAYSIAN PENINSULA DURING MONSOON SEASON

2017 ◽  
Vol XLII-4/W5 ◽  
pp. 165-175
Author(s):  
S. Salihin ◽  
T. A. Musa ◽  
Z. Mohd Radzi
Keyword(s):  
Water Vapour ◽  
Monsoon Season ◽  
Temporal Distribution ◽  
Southwest Monsoon ◽  
Northeast Monsoon ◽  
Path Delay ◽  
Zenith Path Delay ◽  
Temporal Estimation ◽  
Integrated Water Vapour ◽  
Spatio Temporal

This paper provides the precise information on spatial-temporal distribution of water vapour that was retrieved from Zenith Path Delay (ZPD) which was estimated by Global Positioning System (GPS) processing over the Malaysian Peninsular. A time series analysis of these ZPD and Integrated Water Vapor (IWV) values was done to capture the characteristic on their seasonal variation during monsoon seasons. This study was found that the pattern and distribution of atmospheric water vapour over Malaysian Peninsular in whole four years periods were influenced by two inter-monsoon and two monsoon seasons which are First Inter-monsoon, Second Inter-monsoon, Southwest monsoon and Northeast monsoon.

scholarly journals Estimation of precipitable water vapour from GPS during winter season 2003

MAUSAM ◽  
2021 ◽  
Vol 57 (2) ◽  
pp. 323-328
Author(s):  
R. K. GIRI ◽  
B. R. LOE ◽  
N. PUVIARSON ◽  
S. S. BHANDARI ◽  
R. K. SHARMA
Keyword(s):  
Water Vapour ◽  
Winter Season ◽  
Precipitable Water ◽  
New Delhi ◽  
Total Delay ◽  
Precipitable Water Vapour ◽  
Integrated Water Vapour ◽  
Zenith Hydrostatic Delay ◽  
Indian Institute Of Science ◽  
Good Agreement

Lkkj & ok;qeaMy esa ty ok"i dk forj.k LFkkfud :i ls vkSj dkfyd rkSj ij cgqr vf/kd ifjorZu’khy gksrk gSA ty ok"i dk forj.k vusdksa ok;qeaMyh; izfØ;kvksa esa izeq[k Hkwfedk fuHkkrk gSA dqy lekdfyr ty ok"i vFkok le:ih o"kkZ ty ok"i dk vkdyu Xykscy iksft’kfuax flLVe ¼th- ih- ,l-½ tsfuFk VksVy fMys ¼tsM- Vh- Mh-½ ds vk¡dM+ksa dh lgk;rk ls fd;k tk ldrk gSA blesa tsfuFk nzoLFkSfrd fMys ds eku dks funf’kZr fd;k x;k gS vkSj bls tsM- Vh- Mh- ls fudkyus ij tsfuFk vknzZ fMys ds vk¡dM+s izkIr gksaxsA vr% bl izdkj vkdfyr fd, x, tsM- MCY;w- Mh- ds eku ls izk;% yxkrkj ,e- ,e-  esa o"kkZ  ty ok"i dk irk pysxkA bl 'kks/k&i= esa th- ih- ,l- ds vk¡dM+ksa dk mi;ksx djrs gq, ubZ fnYyh ds fy, o"kZ 2003 ds 'khrdkyhu _rq vkSj Hkkjrh; foKku laLFkku ifj"kn] caxykSj ds dsanzksa ds fy, ,e- ,e- esa ih- MCY;w- oh- dk vkdyu djus dk iz;kl fd;k x;k gSA buls izkIr gq, ifj.kkeksa dk jsfM;kslkSUnsa vk¡dM+ksa ds lkFk lgh rkyesy ik;k x;k gSA The distribution of water vapour in atmosphere is highly spatial and temporal variable. It plays a key role in many atmospheric processes. The total integrated water vapour or equivalent precipitable water vapour (PWV) can be estimated with the help of Global Positioning System (GPS) Zenith Total Delay (ZTD) data. The value of Zenith Hydrostatic Delay (ZHD) is modeled and subtracting from ZTD will give Zenith wet delay (ZWD). Consequently, the estimated ZWD values will provide PWV in mm almost in a continuous manner. In this paper an attempt has been made for the estimation of PWV in mm during winter season 2003 for New Delhi and Indian Institute of Science (IISC), Bangalore stations using GPS data. The result shows fairly good agreement with the radio-sonde data. 

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