17 Strengthening Flood and Drought Risk Management Tools …
403
We use the latest version (V7) of the TMPA. The TMPA is a calibration-based
sequential scheme for combining precipitation estimates from multiple satellites, as
well as gauge analyses where feasible, at fine scales (0.25° × 0.25° and 3 hourly).
TMPA is available both after and in real time, based on calibration by the TRMM
combined instrument and TRMM microwave imager precipitation products, respectively. Only the after-real-time product incorporates gauge data. The dataset covers
the latitude band 50°N–S for the period from 1998 to the delayed present. The data
currently contains two products, 3 hourly combined microwave-IR estimates (with
gauge adjustment) and monthly combined microwave-IR-gauge estimates of precipitation computed on quasi-global grids about 2 months after the end of each month
starting in January 1998. We use the 3B43_7 monthly version of the dataset, which
incorporates gauge adjustments, at 0.25° resolution.
b. Soil Moisture
SMAP—Soil Moisture Active Passive
The NASA Soil Moisture Active Passive (SMAP) mission launched in January 2015
was designed for global mapping of soil moisture at a 10-km spatial resolution with
a 2–3-day revisit time under both clear and cloudy sky conditions. This improves
on the resolution relative to AMSR-E (25 km) and SMOS (50 km) by combining an
L-band radar (high resolution 1–3 km, lower accuracy) and an L-band radiometer
(low resolution 40 km, higher accuracy), as well as retrievals for a wider range of
vegetation conditions and for the top 5 cm of the soil. SMAP products also include
level 4 (L4) root-zone estimates by merging SMAP observations with land surface
model estimates via assimilation extending the utility of the data. Unfortunately, the
SMAP radar failed in July 2015 thus restricting soil moisture products to the 40 km
resolution of the radiometer. Here we use monthly mean values that are calculated in
the AFDM based on 3-day moving average data, which are referred to as SMAP-MA.
AMSR-E + VOD
This dataset is based on a retrieval algorithm for daily global soil moisture and
vegetation optical depth (VOD) derived from dual-polarized AMSR-E brightness
temperatures at 10.7 GHz. It uses a simplified radiative transfer model that assumes
(1) the surface to be retrieved is vegetated soil only and (2) the vegetated soil consists
of a smooth bare soil surface plus a layer of vegetation. The model approximates the
output from generally used, but more complex and more rigorously parameterized
radiative transfer models quite well, irrespective of the vegetation density. By incorporating both soil roughness parameters and to-be-retrieved VOD implicitly, the algorithm simplifies the retrieval process since accurate prior knowledge of the global soil
roughness information is unavailable at AMSR-E frequencies and footprint scales.
The data are available globally, for 2002–2009, at 0.25°, daily resolution.
c. Evapotranspiration
GLEAM—Global Land Evaporation Amsterdam Model
403
We use the latest version (V7) of the TMPA. The TMPA is a calibration-based
sequential scheme for combining precipitation estimates from multiple satellites, as
well as gauge analyses where feasible, at fine scales (0.25° × 0.25° and 3 hourly).
TMPA is available both after and in real time, based on calibration by the TRMM
combined instrument and TRMM microwave imager precipitation products, respectively. Only the after-real-time product incorporates gauge data. The dataset covers
the latitude band 50°N–S for the period from 1998 to the delayed present. The data
currently contains two products, 3 hourly combined microwave-IR estimates (with
gauge adjustment) and monthly combined microwave-IR-gauge estimates of precipitation computed on quasi-global grids about 2 months after the end of each month
starting in January 1998. We use the 3B43_7 monthly version of the dataset, which
incorporates gauge adjustments, at 0.25° resolution.
b. Soil Moisture
SMAP—Soil Moisture Active Passive
The NASA Soil Moisture Active Passive (SMAP) mission launched in January 2015
was designed for global mapping of soil moisture at a 10-km spatial resolution with
a 2–3-day revisit time under both clear and cloudy sky conditions. This improves
on the resolution relative to AMSR-E (25 km) and SMOS (50 km) by combining an
L-band radar (high resolution 1–3 km, lower accuracy) and an L-band radiometer
(low resolution 40 km, higher accuracy), as well as retrievals for a wider range of
vegetation conditions and for the top 5 cm of the soil. SMAP products also include
level 4 (L4) root-zone estimates by merging SMAP observations with land surface
model estimates via assimilation extending the utility of the data. Unfortunately, the
SMAP radar failed in July 2015 thus restricting soil moisture products to the 40 km
resolution of the radiometer. Here we use monthly mean values that are calculated in
the AFDM based on 3-day moving average data, which are referred to as SMAP-MA.
AMSR-E + VOD
This dataset is based on a retrieval algorithm for daily global soil moisture and
vegetation optical depth (VOD) derived from dual-polarized AMSR-E brightness
temperatures at 10.7 GHz. It uses a simplified radiative transfer model that assumes
(1) the surface to be retrieved is vegetated soil only and (2) the vegetated soil consists
of a smooth bare soil surface plus a layer of vegetation. The model approximates the
output from generally used, but more complex and more rigorously parameterized
radiative transfer models quite well, irrespective of the vegetation density. By incorporating both soil roughness parameters and to-be-retrieved VOD implicitly, the algorithm simplifies the retrieval process since accurate prior knowledge of the global soil
roughness information is unavailable at AMSR-E frequencies and footprint scales.
The data are available globally, for 2002–2009, at 0.25°, daily resolution.
c. Evapotranspiration
GLEAM—Global Land Evaporation Amsterdam Model