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Precipitable water vapour (PWV) variations as observed using GPS during 2021 forest fres in Southwestern Turkey

Gurbuz Gokhan

Acta Geophysica

2022

Vol. 70, no 4

1937--1946

Devastating forest fires occurred in the southwestern part of Turkey in summer 2021. Besides the fire itself, air quality standards also drastically dropped. Mugla and Antalya were affected the most by the forest fires. Also, precipitable water vapour (PWV) values show different behaviours from the climate typical. Precipitation, temperature, and pressure parameters were investigated, and no anomalies were found. Particulate matters and other pollutants resulting from forest fires were the remaining indicators behind the PWV fluctuations. The relation between PWV and particulate matters from 2.5 to 10 microns (PM10) was investigated at nine Global Positioning System (GPS) stations located at Antalya and Mugla using 15 air quality monitoring stations. The PWV analysis results show a sudden increase in PWV during the forest fires at most GPS stations. After the fires, PWV values decreased over time. However, PWV values were still higher than before the fires. Furthermore, the mean value, the maximum values, and the standard deviation of PM10 during and after the forest fires were investigated. Results show that the PM10 values were in line with the forest fires effects and correlated with the distance between air quality monitoring stations and the forest fire. Most air quality monitoring stations have higher maximum and average PM10 values during the forest fires than after the forest fires. The correlation coefficient between the two datasets shows a high correlation during the forest fires at all the GPS stations. Therefore, results indicate that, as the PM10 concentration increases, PWV values also increase.

Comparison of techniques for Integrated Precipitable Water measurement in the polar region

Kruczyk M.

Geoinformation Issues

2015

Vol. 7, no. 1(7)

15--27

Tropospheric delay estimates (tropospheric product) for selected International GNSS Service (IGS) and EUREF Permanent Network (EPN) stations made it possible to asses two areological techniques in the polar region (mainly in Greenland). Integrated Precipitable Water (IPW) – important meteorological parameter is derived from GPS tropospheric solutions by a known procedure for GPS stations. To convert from the wet part of tropospheric delay (ZWD) to IPW, the relation between 2 m temperature and the so-called mean temperature of the atmosphere above was derived using local radiosonde data for nearby GPS stations. Sunphotometer data were provided by AERONET (NASA AErosol RObotic NETwork). IPW comparisons lead to the determination of a systematic difference between the techniques of GPS IPW and sunphotometer data (not present in the case of RAOBs). IPW measured by sunphotometer CIMEL (Cimel Electronique) is several percent smaller than IPW from GPS (both IGS and EPN solution). The bias changes seasonally and is a function of atmospheric temperature. It signals some systematic deficiencies in solar photometry as the IPW retrieval technique. CIMEL IPW shows some temperature dependent bias also in relation to radiosoundings.

Rozwiązania troposferyczne IGS i EPN zostały wykorzystane do przetestowania dwu technik pomiarów aerologicznych dla stacji GNSS w regionie polarnym (Grenlandia). Parametr meteorologiczny jakim jest scałkowana zawartość pary wodnej (IPW) został pozyskany za pomocą standardowej procedury opisanej w literaturze. Do przeliczania IPW z wilgotnej części opóźnienia opracowano lokalny model temperatury średniej (zależność linowa względem temperatury na wysokości 2 metrów nad powierzchnią ziemi) wyznaczony z radiosondowań prowadzonych w sąsiedztwie stacji GNSS. Pomiary fotometryczne udostępnia sieć pomiarów aerozoli AERONET działająca pod egidą NASA. Porównania kilkuletnich szeregów IPW wykazują systematyczne różnice między IPW z GNSS a fotometrem słonecznym (ale nie radiosondażem). IPW z fotometru jest nie tylko średnio kilka procent mniejsza niż z GNSS ale różnica ta zmienia się wraz z porami roku i temperaturą (co jest szczególnie widoczne w warunkach polarnych). To wykazuje pewien istotny problem z fotometrią słoneczną jako techniką pomiarów kolumnowej pary wodnej. Fotometr wykazuje systematyczną różnicę IPW (zależną od temperatury atmosferycznej) także w stosunku do wyników radiosondażu.