التفاصيل البيبلوغرافية
| العنوان: |
Surface Water Temperature Heterogeneity at Subpixel Satellite Scales and Its Effect on the Surface Cooling Estimates of a Large Lake: Airborne Remote Sensing Results From Lake Geneva. |
| المؤلفون: |
Irani Rahaghi, Abolfazl, Lemmin, Ulrich, Barry, David Andrew |
| المصدر: |
Journal of Geophysical Research. Oceans; Jan2019, Vol. 124 Issue 1, p635-651, 17p |
| مصطلحات موضوعية: |
WATER temperature, REMOTE sensing, LAKES, CLIMATE change, WEATHER forecasting |
| مستخلص: |
The dynamics of spatial heterogeneity of lake surface water temperature (LSWT) at subpixel satellite scale O(1 m) and its effect on the surface cooling estimation at typical satellite pixel areas O(1 km2) were investigated using an airborne platform. The measurements provide maps that revealed spatial LSWT variability with unprecedented detail. The cold season data did not show significant LSWT heterogeneity and hence no surface cooling spatial variability. However, based on three selected daytime subpixel‐scale maps, LSWT patterns showed a variability of >2 °C in the spring and >3.5 °C in the summer, corresponding to a spatial surface cooling range of >20 and >40 W/m2, respectively. Due to the nonlinear relationship between turbulent surface heat fluxes and LSWT, negatively skewed LSWT distributions resulted in negatively skewed surface cooling patterns under very stable or predominantly unstable atmospheric boundary layer (ABL) conditions and positively skewed surface cooling patterns under predominantly stable ABL conditions. Implementing a mean spatial filter, the effect of area‐averaged LSWT on the surface cooling estimation up to a typical satellite pixel was assessed. The effect of the averaging filter size on the mean spatial surface cooling values was negligible, except for predominantly stable ABL conditions. In that situation, a reduction of ~3.5 W/m2 was obtained when moving from high O(1 m) to low O(1 km) pixel resolution. Plain Language Summary: Lake surface water temperature (LSWT) is one of the main parameters required for estimating surface cooling at the air‐water interface and is also essential for understanding other processes (such as ecosystem dynamics, climate change, and numerical weather prediction) in lakes. Usually, surface cooling is determined from in situ point measurements or satellite images. Satellite thermal images resolve surface areas with a typical pixel resolution of O(1 km). Therefore, satellite data can depict large‐scale thermal patterns. But can LSWT spatial variability be significant at subpixel satellite resolution over a large lake? What is the effect of such variability on area‐averaged surface cooling estimates? To address these questions, a measurement system, including a balloon‐launched airborne platform for thermography and a catamaran for in situ measurements along predefined tracks, was used for LSWT mapping and calibration. Surface cooling patterns were then estimated using a calibrated bulk model. Results showed insignificant LSWT heterogeneity and hence no surface cooling spatial variability during the cold seasons. However, a notable spatial variability of >2 °C and > 3.5 °C was found in spring and summer, respectively. The effect of LSWT heterogeneity on surface cooling variability was significant, in particular, when air‐water temperature differences were close to 0. Key Points: Airborne surface water temperature heterogeneity patterns on a lake resolved at subpixel satellite scale (1‐m resolution) are presentedThe surface cooling distribution can be different from the surface water temperature distribution under predominantly stable conditionsThe surface water temperature heterogeneity influences the area‐averaged surface cooling estimates under near‐neutral conditions [ABSTRACT FROM AUTHOR] |
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