Applicability of GRACE and GRACE-FO for monitoring water mass changes of the Aral Sea and the Caspian Sea

Abstract

The GRACE gravity satellite mission has provided monthly gravity field solutions for about 15 years enabling a unique opportunity to monitor large scale mass variation processes. By the end of the GRACE, the GRACE-FO mission was launched in order to continue the time series of monthly gravity fields. The two missions are similar in most aspects apart from the improved intersatellite range rate measurements, which is performed with lasers in addition to microwaves. An obvious demand for the geoscientific applications of the monthly gravity field models is to understand the consistency of the models provided by the two missions. This study provides a case-study related consistency investigation of GRACE and GRACE-FO monthly solutions for the Aral Sea region. As the closeness of the Caspian Sea may influence the monthly mass variations of the Aral Sea, it has also been involved in the investigations. According to the results, GRACE-FO models seem to continue the mass variations of the GRACE period properly, therefore their use jointly with GRACE is suggested. Based on the justified characteristics of the gravity anomaly by water volume variations in the case of the Aral Sea, GRACE models for the period March–June 2017 are suggested to be neglected. Though the correlation between water volume and monthly gravity field variations is convincing in the case of the Aral Sea, no such a correlation for the Caspian Sea could have been detected, which suggests to be the consequence of other mass varying processes, may be related to the seismicity of the Caspian Sea area.

Gravity variations determined from GRACE and GRACE-FO monthly solutions for analyzing water mass changes in the Aral Sea

“…This study is a continuation and a refinement of the work of Földváry et al [5]. According to Figure 6 of Földváry et al [5] in the reservoir of the Aral Sea, the correlation between water volume change and gravity anomaly was found to be 0.8636, which is a quite convincing relationship.…”

“…This study is a continuation and a refinement of the work of Földváry et al [5]. According to Figure 6 of Földváry et al [5] in the reservoir of the Aral Sea, the correlation between water volume change and gravity anomaly was found to be 0.8636, which is a quite convincing relationship. However, from 2002 to about mid-2005, an increase in gravity anomaly was determined, which is opposite to the water volume change tendencies.…”

“…In Földváry et al [5] gravity anomaly time series have been determined for the period of April 2002 to November 2019. The present study has been extended until January 2022.…”

“…Subsequently, a linear trend on the resulting time series has been fitted to capture longterm mass variations. The resulting trends are visualized in Figure 1 [5]. Clearly, mass variations of the Caspian Sea have an impact on the gravity anomaly variations of the Aral Sea.…”

Soil Salinity Monitoring in Irrigated Areas of Rishtan District of Ferghana Valley, Uzbekistan

“…In particular, 11.5% of 1.08 million ha of irrigated land in Kyrgyzstan, 16.0% of 719,200 ha in Tajikistan, 33.0% of 2.31 million ha in Kazakhstan, 95.9% of 1.74 million ha in Turkmenistan, and around 50% of 4.28 million ha in Uzbekistan are prone to soil salinization at different levels [7][8]. Many scientists and experts in developed and developing countries have studied the relationship between the salinity levels of irrigated areas and groundwater levels and its mineralization, and other anthropogenic influences using and comparing GIS-based methods (interpolation, vegetation, and hydrological indices) [9][10][11].…”