Chapter 13
A BIOPHYSICAL PROCESS-BASED ESTIMATE
OF GLOBAL LAND SURFACE EVAPORATION
USING SATELLITE AND ANCILLARY DATA
B. Choudhury
NASA Goddard Space Flight Center, Greenbelt, MD, USA.
1. INTRODUCTION
The rich history and many fundamental investigations of the global land
surface evaporation can be found in Korzun (1978), and Korzun’s
monograph can also provide an appreciation of the care and the effort
involved in such investigations. Recent contributions include those by
Willmott et al. (1985), Henning (1989), Mintz and Walker (1993) and Oki et
al. (1995). These investigations, except for Oki et al. (1995), are based upon
long-term average surface meteorological observations and, in some cases,
river runoff data.
Fig. 1 shows zonal average values of annual total evaporation calculated
by Baumgartner and Reichel (1975) and Henning (1989) in 5° latitude bands
and by Budyko (1978) in 10° latitude bands. One could point to both
remarkable agreements and noticeable differences seen in this figure. These
calculations provide references for climatological evaporation.
Significant changes of land surface characteristics have occurred and are
still continuing, and field observations show that these changes affect the
partitioning of available energy and precipitation at the land surface. The
representativeness of the previous evaporation values for the present state of
the land surface has not yet been assessed. A biophysical process-based
model is needed to account for the impact of land surface change on
evaporation.
119
M.M. Verstraete et al. (eds.), Observing Land from Space: Science, Customers and Technology, 119–126.
© 2000 Kluwer Academic Publishers. Printed in the Netherlands.
A BIOPHYSICAL PROCESS-BASED ESTIMATE
OF GLOBAL LAND SURFACE EVAPORATION
USING SATELLITE AND ANCILLARY DATA
B. Choudhury
NASA Goddard Space Flight Center, Greenbelt, MD, USA.
1. INTRODUCTION
The rich history and many fundamental investigations of the global land
surface evaporation can be found in Korzun (1978), and Korzun’s
monograph can also provide an appreciation of the care and the effort
involved in such investigations. Recent contributions include those by
Willmott et al. (1985), Henning (1989), Mintz and Walker (1993) and Oki et
al. (1995). These investigations, except for Oki et al. (1995), are based upon
long-term average surface meteorological observations and, in some cases,
river runoff data.
Fig. 1 shows zonal average values of annual total evaporation calculated
by Baumgartner and Reichel (1975) and Henning (1989) in 5° latitude bands
and by Budyko (1978) in 10° latitude bands. One could point to both
remarkable agreements and noticeable differences seen in this figure. These
calculations provide references for climatological evaporation.
Significant changes of land surface characteristics have occurred and are
still continuing, and field observations show that these changes affect the
partitioning of available energy and precipitation at the land surface. The
representativeness of the previous evaporation values for the present state of
the land surface has not yet been assessed. A biophysical process-based
model is needed to account for the impact of land surface change on
evaporation.
119
M.M. Verstraete et al. (eds.), Observing Land from Space: Science, Customers and Technology, 119–126.
© 2000 Kluwer Academic Publishers. Printed in the Netherlands.