Long‐term variability and trends of precipitable water vapour derived from GPS tropospheric path delays over the Eastern Mediterranean

Abstract

The precipitable water vapour (PWV) of 21 Global Navigation Satellite System (GNSS) ground receivers from the Survey Of Israel Active Permanent Network (SOI-APN) in the Eastern Mediterranean area are processed and analysed. We focus on the annual cycles, inter-annual variations and long-term trends. The PWV monthly mean values peak during September-October where October has the highest variability for all stations. PWV values reach minimum level during February-March where Apr is the least variable month for most stations. Generally, the PWV variability decreases with station height. Additionally, harmonic analysis indicates that the annual mode's amplitude decreases with station height. In contrast, the semi-annual mode's accounting for the sub-annual variance increases with station height. The PWV monthly mean anomalies are consistent among all the stations suggesting a common regional driver. Furthermore, a comparison between the PWV station average anomalies and the regional mean anomalies from the ERA5 reanalysis shows a strong correlation with r = 0.95. In addition, a correlation coefficient of r = 0.72 was found with the regional mean moisture flux anomalies at 750 hPa taken from ERA5 and the station average PWV anomalies, thus implying that horizontal moisture flow accounts for most of the inter-annual variability. However, the significance of the 750 hPa pressure level requires future investigation. For the long-term analysis, we find an increasing regional mean trend of 0.5 mm Á decade −1 for the entire data period (1997-2019) as compared to 1 mm Á decade −1 for the last decade (2010-2019) suggesting a recent accelerated moistening of the Eastern Mediterranean region.

Tropospheric Delay in the Neapolitan and Vesuvius Areas (Italy) by Means of a Dense GPS Array: A Contribution for Weather Forecasting and Climate Monitoring

“…Unlike temperature, the precipitation regime shows neither pronounced nor unambiguous trends over the Italian regions. Accounting for the previous considerations, we guess that the trends observed in GPS-retrieved PWV might be ruled by a general temperature increase, as was even found by Alshawaf et al [41] in Germany (Central Europe), but we cannot exclude that there could also be feedback with synoptic mode variability in the region, as found by Ziv et al [42], over the Eastern Mediterranean area. The retrieved increment in PWV (about 2 mm/decade) around 7 ÷ 9% of the mean PWV is comparable to the theoretical rate of the Clausius-Clapeyron gradient.…”

“…Since the Neapolitan area is near the Mediterranean Sea, we can compare our results with other studies that analyze PWV in this type of climate. Ziv et al [42], in Israel, have shown that the PWV long-term trend for 1998-2019 is~0.5 mm decade −1 while it is 1.1 mm decade −1 for 2010-2019 interval. Ziv et al [42] speculate that the PWV increase, in the last decade, is due to the response to an increasing temperature signal.…”

“…Ziv et al [42], in Israel, have shown that the PWV long-term trend for 1998-2019 is~0.5 mm decade −1 while it is 1.1 mm decade −1 for 2010-2019 interval. Ziv et al [42] speculate that the PWV increase, in the last decade, is due to the response to an increasing temperature signal. Based on the analyses of time series collected on globally distributed 150 IGS stations (1994-2006), Jin et al [43] investigated the secular trend and seasonal variation of zenith tropospheric delay (ZTD), as well as its implications for the climate.…”

Impacts of Non-Local versus Local Moisture Sources on a Heavy (and Deadly) Rain Event in Israel

“…Here, the PWV data were extracted from 21 GPS ground stations belonging to the Survey of Israel Active Permanent Network (SOI-APN). For a more detailed description of the methodology, see Ziskin Ziv et al [23,24]. Six daily values are presented below.…”

Validation of FY-3D MERSI-2 Precipitable Water Vapor (PWV) Datasets Using Ground-Based PWV Data from AERONET

“…Water vapor is one of the most important sources of the greenhouse effect [1], as well as a key factor affecting precipitation, severe weather and the global energy cycle [2][3][4]. Although water vapor only accounts for a small part of the total atmosphere, it plays an important role in the earth's weather system and climate change.…”