Improvements in mountain lake monitoring from satellite altimetry over the past 30 years – lessons learned from Tibetan lakes

Jiang，Liguang1; Nielsen，Karina2; Andersen，Ole B.2

2023-09-01

10.1016/j.rse.2023.113702

Remote Sensing of Environment   Impact Factor & Quartile

0034-4257

1879-0704

Satellite altimetry has been widely used for inland water monitoring and modeling in the present decade. In this paper, the availability, data quality, and quantity of a number of spaceborne radar altimetry missions (including Topex/Poseidon (TP), ERS-2, Envisat, Jason-1/−2/−3, CryoSat-2, Saral, and Sentinel-3) are investigated. This is, to the best of our knowledge, the first paper to investigate the influences of onboard trackers, satellite flying directions, and land contamination on Level-1 waveforms and Level-2 measurements over large mountainous lakes. The analyses were conducted over eight Tibetan lakes, which are of varying sizes from ca. 93 to 1046 km and are sampled by multiple altimeters. From the results presented in this paper, it is demonstrated that the previous generation of altimeters, such as TP, Jason-1, ERS-2, and Envisat, shows a higher percentage of data unavailability and lower valid observation rates. Investigations of Level-1 waveforms show onboard tracker failing in locking on the lake surface, resulting in data loss or invalid measurements. In addition, the onboard tracking systems are sometimes unstable, resulting in larger along-track standard deviations (SD) (SD > 15 cm). In contrast, the recent generation of altimeters, i.e., Jason-3 and Sentinel-3 with open-loop tracking mode, significantly increases the data availability (> 90% passes and > 60% individual observations) and delivers higher precision measurements (SD around 10 cm). Moreover, the waveform leading edge is very consistent, indicating more stable onboard tracking. Higher quality Jason-3 and Sentinel-3 data allow monitoring of sub- and quasi-monthly lake variations, which are not revealed by e.g., TP and ERS-2 data due to poorer signal-to-noise ratios. Exceptionally, Saral Ka-band altimeter, operated in closed-loop tracking mode, is less affected by flying directions and land contamination (topography and landscapes), delivering high quality measurements (SD around 7 cm for 40 Hz). This study provides a comprehensive comparison of multiple altimeters in monitoring lakes in mountainous areas, and demonstrates the substantial improvements achieved in the past decades. However, care has to be taken when merging data from old generation altimetry missions over mountainous lakes. The lessons learned from these Tibetan lakes can be taken across to other mountain lakes.

Colsed-loop CryoSat-2 Envisat ERS Jason-1/-2/-3 Mountainous lake Onboard tracker Open-loop Radar altimetry Range window SARAL/AltiKa Sentinel-3 Tibetan Plateau Topex/Poseidon Waveform

SCI

English

First ; Corresponding

Danida Fellowship Centre[18-M01-DTU];Danida Fellowship Centre[CKWV20221009];Danida Fellowship Centre[Y01296129];Danida Fellowship Centre[Y01296229];

Environmental Sciences & Ecology ; Remote Sensing ; Imaging Science & Photographic Technology

Environmental Sciences ; Remote Sensing ; Imaging Science & Photographic Technology

WOS:001035574200001

ELSEVIER SCIENCE INC

GEOSCIENCES

2-s2.0-85163200570

Scopus

1.School of Environmental Science and Engineering,Southern University of Science and Technology,Shenzhen,China
2.DTU Space - National Space Institute,Technical University of Denmark,Kgs. Lyngby,Denmark

Jiang，Liguang,Nielsen，Karina,Andersen，Ole B.. Improvements in mountain lake monitoring from satellite altimetry over the past 30 years – lessons learned from Tibetan lakes[J]. Remote Sensing of Environment,2023,295.

Jiang，Liguang,Nielsen，Karina,&Andersen，Ole B..(2023).Improvements in mountain lake monitoring from satellite altimetry over the past 30 years – lessons learned from Tibetan lakes.Remote Sensing of Environment,295.

Jiang，Liguang,et al."Improvements in mountain lake monitoring from satellite altimetry over the past 30 years – lessons learned from Tibetan lakes".Remote Sensing of Environment 295(2023).