410
T. J. Ballatore et al.
a repeat time of 15 days, this technique has been applied successfully to determine
water level (volume) changes in some of the larger African lakes.
A number of papers have looked at the water balance of Lake Victoria whose
dramatic decline in lake water coinciding with the completion of a second dam on
the outflowing river in 1999 in Uganda. Awange et al. (2008) used changes in geoidal
variation as measured by GRACE to show an annual loss of 1.6 mm/yr in the lake
basin from 2002 to 2006. This information, coupled with Tropical Rainfall Measuring
Mission (TRMM) and the Challenging Minisatellite Payload (CHAMP) indicated
that dam operations were the likely cause in the decline in lake level with respect
to precipitation (TRMM) or evaporation (CHAMP). This conclusion was confirmed
by Swenson and Wahr (2009) using GRACE, altimetric lake level data remotelysensed data on precipitation (TRMM) and evaporation, including wind speed from
the scatterometer SeaWinds, onboard the QuikSCAT satellite; temperature from the
MODIS Aqua; and near-surface temperature and humidity from the Advanced Microwave Sounding Unit (AMSU-A), the Special Sensor Microwave Imager (SSM/I)
and the Special Sensor Microwave/ Temperature & Humidity Profile (SSM/T2).
Becker et al. (2010) used GRACE measurements of changes in terrestrial water
storage, altimetrically-sensed changes in lake level, and Global Precipitation Climatology Centre (GPCC) data on precipitation to show common modes of variability
among the levels of Lakes Malawi, Tanganyika, Turkana and Victoria due to the effect of the Indian Ocean Dipole (IOD) and El Niño-Southern Oscillation from 2003
to 2008.
As part of a large-scale study of hydrological variations in Africa, Boy et al.
(2012) compared GRACE-based estimates of water level change with altimetric
data for Lakes Malawi, Tanganyika and Victoria. They showed that spherical harmonic solutions, while suitable for Lake Victoria, do not perform as well for lakes
with a narrow east-west extent such as Malawi and Tanganyika. For the latter, they
recommend localized approaches such as mascons. Work was also done by Boy et al.
(2012) and Hinderer et al. (2012) on the Lake Chad basin but the GRACE data were
not linked to lake level, undoubtedly due to the very small volume of water contained
in Lake Chad.
20.4 Lake Properties: Physical
20.4.1 Thermal Sensing of Surface Temperature
Schneider et al. (1985), in addition to visible, NIR and thermal work to delineate
water extent discussed above, also produced a surface water temperature map for
Lake Chad and the surrounding area using daytime observations with Channels 4
and 5 of the AVHRR sensor. They applied a two atmospheric window approach
from McClain (1981) and were able to demonstrate distinct and large temperature
differences among the lake regions and surrounding terrain including inflowing river
deltas.
T. J. Ballatore et al.
a repeat time of 15 days, this technique has been applied successfully to determine
water level (volume) changes in some of the larger African lakes.
A number of papers have looked at the water balance of Lake Victoria whose
dramatic decline in lake water coinciding with the completion of a second dam on
the outflowing river in 1999 in Uganda. Awange et al. (2008) used changes in geoidal
variation as measured by GRACE to show an annual loss of 1.6 mm/yr in the lake
basin from 2002 to 2006. This information, coupled with Tropical Rainfall Measuring
Mission (TRMM) and the Challenging Minisatellite Payload (CHAMP) indicated
that dam operations were the likely cause in the decline in lake level with respect
to precipitation (TRMM) or evaporation (CHAMP). This conclusion was confirmed
by Swenson and Wahr (2009) using GRACE, altimetric lake level data remotelysensed data on precipitation (TRMM) and evaporation, including wind speed from
the scatterometer SeaWinds, onboard the QuikSCAT satellite; temperature from the
MODIS Aqua; and near-surface temperature and humidity from the Advanced Microwave Sounding Unit (AMSU-A), the Special Sensor Microwave Imager (SSM/I)
and the Special Sensor Microwave/ Temperature & Humidity Profile (SSM/T2).
Becker et al. (2010) used GRACE measurements of changes in terrestrial water
storage, altimetrically-sensed changes in lake level, and Global Precipitation Climatology Centre (GPCC) data on precipitation to show common modes of variability
among the levels of Lakes Malawi, Tanganyika, Turkana and Victoria due to the effect of the Indian Ocean Dipole (IOD) and El Niño-Southern Oscillation from 2003
to 2008.
As part of a large-scale study of hydrological variations in Africa, Boy et al.
(2012) compared GRACE-based estimates of water level change with altimetric
data for Lakes Malawi, Tanganyika and Victoria. They showed that spherical harmonic solutions, while suitable for Lake Victoria, do not perform as well for lakes
with a narrow east-west extent such as Malawi and Tanganyika. For the latter, they
recommend localized approaches such as mascons. Work was also done by Boy et al.
(2012) and Hinderer et al. (2012) on the Lake Chad basin but the GRACE data were
not linked to lake level, undoubtedly due to the very small volume of water contained
in Lake Chad.
20.4 Lake Properties: Physical
20.4.1 Thermal Sensing of Surface Temperature
Schneider et al. (1985), in addition to visible, NIR and thermal work to delineate
water extent discussed above, also produced a surface water temperature map for
Lake Chad and the surrounding area using daytime observations with Channels 4
and 5 of the AVHRR sensor. They applied a two atmospheric window approach
from McClain (1981) and were able to demonstrate distinct and large temperature
differences among the lake regions and surrounding terrain including inflowing river
deltas.