Abstract
The present paper investigates precipitable water vapor (PWV) variations over the lower middle latitude Turkish region from the International GNSS Services (IGS) and Turkish Permanent GNSS Network (TPGN) observations. The diurnal, seasonal, annual, and rainfall time behavior of PWV and their relative deviations are presented covering the period from 2009 to 2017. Additionally, the predictions from Auto Regressive Moving Average (ARMA) model and ERA-Interim reanalysis datasets are analyzed to understand their effectiveness over the region. In the first observation, diurnal profile indicates maximum value of PWV over the ocean climate regions whereas minimum value is noticed over the semi-arid continental climate areas of Turkey. The seasonal maximum value of PWV is observed in June solstice followed by September equinox and the lowest value is seen in December solstice followed March equinox. The studies also cover annual variation, grand-mean of tropospheric PWV and PWV intensity from the TPGN confirming the range of PWV between 0 to 45 mm. The PWV time series during 2009 to 2017 exhibit a strong annual variation at all sites, with distinctive peaks and dips occurring approximately in summer and winter, respectively. The precipitation plots displayed a clear increasing pattern in summer but the values are less in winter. However, the annual relative deviation of PWV lies in the range of − 0.5 to 1.5 units for all stations. The highest grand-mean of PWV is registered in 2010 (~ 22 mm) whereas the lowest value is seen in 2011 (~ 11 mm). The spatial variation of PWV shows that the northern boundary of the Turkey, western part of the country and Northern Cyprus have higher magnitude of PWV while the other part of the country like Central and Eastern Turkey have the lower magnitudes of PWV. PWV analysis during the precipitation period reconfirms that the rainfall pattern is not necessary to follow the PWV time series due to interlinked atmospheric processes. However, we found the PWV predictability of ARMA model is relatively better than the ERA-Interim model. Comprehensive analysis of TPGN data over the region may complement towards a better understanding of the tropospheric dynamics, their effects and the future refinements of atmospheric models over the lower middle latitude Turkish region.
Highlights
The troposphere is the lowermost layer of earth’s atmosphere extending approximately 7 to 20 km from the earth’s surface where almost all weather takes place
The tropospheric delay is known as the Zenith Total Delay (ZTD) and can be distinguished into two components, namely the Zenith Wet Delay (ZWD) that corresponds to the moisture content of the atmosphere and the Zenith Hydrostatic Delay (ZHD) or Zenith Dry Delay (ZDD) caused by dry air gases in the atmosphere
Here, we investigated the behavior of precipitable water vapor (PWV) variations estimated from Global Navigation Satellite System (GNSS) stations in terms of diurnal, seasonal, annual and as well as spatial domain
Summary
The troposphere is the lowermost layer of earth’s atmosphere extending approximately 7 to 20 km from the earth’s surface where almost all weather takes place. The variation of PWV effect obtained from GNSS stations are compared with their corresponding PWV values from ERA-Interim and ARMA models (Fig. 6). The time series of the nine-year PWV estimation depict strong annual variation in PWV at all sites, Fig. 7 The monthly RMSE values between the a ERA-Interim, b ARMA model predicted PWV and observed GNSS-PWV over ISTA, ZONG, IZMI, HATA, KNYA, BING and ANTE of average values of the years 2009, 2012 and 2016
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