The document discusses the use of satellite soil moisture data for rainfall estimation through a new approach called 'sm2rain'. It highlights the algorithm's performance in estimating rainfall accurately by integrating multiple satellite soil moisture products and compares it with traditional methods. The results indicate significant improvement in rainfall estimation, especially beneficial for flood and drought management.

1. http://hydrology.irpi.cnr.it
22 nd Sept. 2016
Luca Brocca, Angelica Tarpanelli, Luca Ciabatta,
Christian Massari, Paolo Filippucci, Amarnath Giriraj,
Wolfgang Wagner
3rd Satellite Soil Moisture
Validation and Application Workshop

2. Remote sensing of rainfall
RAINGAUGE DENSITY
1 degree resolution
CPC dataset
0
2
1
5
10
REVISIT TIME
# SATELLITES

3. The GPM constellation
Synthetic
data
Observed
data
The retrieval approach used in GPM is based on a “top-down” approach providing
an estimate of the INSTANTANEOUS RAINFALL RATE at the satellite overpass
At least, 10 passes per day
are needed for obtaining
satisfactory performance
in estimating 1-day rainfall
WHY GPM IS SO SUCCESSFUL IN BUILDING A CONSTELLATION?

4. SM2RAIN: a new “bottom-up” approach!
SM2RAIN is a new “bottom-up” approach (Brocca et al., 2014
JGR) for estimating the ACCUMULATED RAINFALL from satellite
(and in situ) soil moisture observations

5. precipitation
surface runoff
evapotranspiration
drainage
soil water
capacity
relative saturation
Inverting for p(t):
= soil depth X porosity
Assuming: + +
ONLY during rainfall
Soil water balance equation
SM2RAIN algorithm
1 equation, 3 parameters (Z,a,b)…very SIMPLE!

6. An example with SMAP soil moisture data
Red dots: SMAP Level-2 retrievals (descending)
Blue histogram: gauge-based rainfall time series
(Western U.S.)
A lot of rain: SM goes up a lot
A little rain: SM goes up a little
Just published on WRR: 1st SM2RAIN application to SMAP observations
R² map
(1-degree, 5-day)

7. SM2RAIN application to multiple products

8. SM2RAIN application to multiple products

9. Metop-A
Blu: MetopA+MetopB
Red: MetopA
Black: rainfall
Rainfall events not detected by Metop-A only and
correctly identified by using both Metop-A and Metop-B
Metop-B
What is the potential of a constellation?

10. A soil moisture constellation!
What is the benefit coming
from the integration of multiple
satellite soil moisture product
for SM2RAIN application?
 How to perform the integration?
 Which
product/algorithm/band/orbit to
include?
 What spatial/temporal sampling?

11. Ground and satellite rainfall datasets
India Meteorological Department (IMD)
rainfall dataset (1901-currrent)
Currently (freely) available
satellite soil moisture products
2012 2013 2014 2015 2016
J A J O J A J O J A J O J A J O J A J O
ASCAT
Metop-A
ASCAT
Metop-B
AMSR2
SMOS
SMAP
RapidScat
 Period: 1-April-2015  31-December-2015
 Spatial/temporal resolution: 0.25°/1-day
 Integration at RAINFALL LEVEL (minimization RMSE)
 ASCAT: Metop-A+Metop-B
 AMSR2: LPRM algorithm, X-band
 AMSR2&SMOS: separately asc. and desc. orbits
 RapidScat: separately HH and VV polarization
A similar analysis was also carried out in Italy, results available at http://dx.doi.org/10.13140/RG.2.2.24296.67848

12. Performance of single products
5-day correlation maps
 Low performance in northern India (Himalaya)
 ASCAT, SMAP and AMSR2 performs very good (median R>0.78)
 RapidScat is performing less good, likely due to vegetation
 SMOS is affected by RFI (mainly ascending orbit) during 2015 in India

13. Merging multiple SM prods: R and RMSE
3-day and 5-day correlation maps

14. Rainfall timeseries
 Underestimation of large
rainfall events due to the
saturation problem
 Overestimation of low
rain rates due to noise in
satellite soil moisture
products

15. Comparison with GPM early and final run
1. Significantly better
performance than GPM
products, also of the final run
(gauge-corrected)
2. Product potentially available
in near real-time (large
potential for flood, drought,
landslide applications)
GPM
final run
GPM
early run
SM2RAIN-
multiple SM

16. # Journal Year Reference Short description
1 GRL 2013
Brocca, L., Melone, F., Moramarco, T., Wagner, W. (2013). A new method for rainfall estimation through soil moisture observations.
Geophysical Research Letters, 40(5), 853-858.
First application of SM2RAIN to in situ and satellite data
(some locations)
2 JGR 2014
Brocca, L., Ciabatta, L., Massari, C., Moramarco, T., Hahn, S., Hasenauer, S., Kidd, R., Dorigo, W., Wagner, W., Levizzani, V. (2014).
Soil as a natural rain gauge: estimating global rainfall from satellite soil moisture data. Journal of Geophysical Research, 119(9), 5128-
5141.
SM2RAIN application to ASCAT, AMSR-E and SMOS soil
moisture products on a global scale
3 AWR 2014
Massari, C., Brocca, L., Moramarco, T., Tramblay, Y., Didon Lescot, J.-F. (2014). Potential of soil moisture observations in flood
modelling: estimating initial conditions and correcting rainfall. Advances in Water Resources, 74, 44-53.
Improving runoff prediction by using SM2RAIN-derived
rainfall applied to in situ observations (France)
4 JHH 2015
Brocca, L., Massari, C., Ciabatta, L., Moramarco, T., Penna, D., Zuecco, G., Pianezzola, L., Borga, M., Matgen, P., Martínez-Fernández,
J. (2015). Rainfall estimation from in situ soil moisture observations at several sites in Europe: an evaluation of SM2RAIN algorithm.
Journal of Hydrology and Hydromechanics, 63(3), 201-209.
Detailed analysis of SM2RAIN algorithm in 10 sites over
Europe (testing of different formulations)
5 JHM 2015
Ciabatta, L., Brocca, L., Massari, C., Moramarco, T., Puca, S., Rinollo, A., Gabellani, S., Wagner, W. (2015). Integration of satellite soil
moisture and rainfall observations over the Italian territory. Journal of Hydrometeorology, 16(3), 1341-1355.
Integration of top-down (TRMM 3B42RT) and bottom-up
(SM2RAIN) approaches over Italy
6 JAG 2016
Ciabatta, L., Brocca, L., Massari, C., Moramarco, T., Gabellani, S., Puca, S., Wagner, W. (2016). Rainfall-runoff modelling by using
SM2RAIN-derived and state-of-the-art satellite rainfall products over Italy. International Journal of Applied Earth Observation and
Geoinformation, 48, 163-173.
Improving runoff prediction by using SM2RAIN-derived
rainfall applied to satellite observations (4 basins in Italy)
7 JSTARS 2016
Brocca, L., Massari, C., Ciabatta, L., Wagner, W., Stoffelen, A. (2016). Remote sensing of terrestrial rainfall from Ku-band
scatterometers. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 9(1), 533-539.
Application of SM2RAIN to Ku-band scatterometer data
(RapidSCAT) in central Italy
8 ATMRES 2016
Abera, W., Brocca, L., Rigon, R. (2016). Comparative evaluation of different satellite rainfall estimation products and bias correction in
the Upper Blue Nile (UBN) basin. Atmospheric Research, 178-179, 471-483.
Application of SM2RAIN to ESA CCI soil moisture product
in Ethiopia
9 WRR 2016
Koster, R.D., Brocca, L., Crow, W.T., Burgin, M.S., De Lannoy, G.J.M. (2016). Precipitation Estimation Using L-Band and C-Band Soil
Moisture Retrievals. Water Resources Research, in press.
Application of SM2RAIN to SMAP, SMOS and ASCAT on
a global scale
10 JGR
Minor
rev
Brocca, L., Pellarin, T., Crow, W.T., Ciabatta, L., Massari, C., Ryu, D., Su, C.-H., Rudiger, C., Kerr, Y. (...). Rainfall estimation by inverting
SMOS soil moisture estimates: a comparison of different methods over Australia. submitted to Journal of Geophysical Research.
Application of three methods for rainfall estimation from
SMOS in Australia
11 HESS Subm.
Abera, W., Formetta, G., Brocca, L., Rigon, R. (...). Water budget modelling of the Upper Blue Nile basin using the JGrass-NewAge
model system and satellite data. Hydrology and Earth System Sciences Discussion, in review, doi:10.5194/hess-2016-290.
http://dx.doi.org/10.5194/hess-2016-290
Use of SM2RAIN rainfall for water budget modelling in
ungauged areas
12 JoH
Minor
rev.
Ciabatta, L., Marra, A.C., Panegrossi, G., Casella, D., Sanò, P., Dietrich, S., Massari, C., Brocca, L. (...) Analysis of daily rainfall over Italy
from satellite microwave-based precipitation products. submitted to Journal of Hydrology.
Integration of top-down (CDRD-PNPR) and bottom-up
(SM2RAIN) approaches over Italy, an update
13 JSTARS Subm.
Brocca, L., Crow, W.,T. Ciabatta, L., Massari, C., de Rosnay, P., Enenkel, M., Hahn, S., Amarnath, G., Camici, S., Tarpanelli, A.,
Wagner, W. (...). A review of the applications of scatterometer soil moisture data. submitted to IEEE Journal of Selected Topics in
Applied Earth Observations and Remote Sensing.
Review of scatterometer soil moisture applications with
recent results of SM2RAIN
1 TCD 2014
Pan, X., Yu, Q., and You, Y. (2014). Role of rainwater induced subsurface flow in water-level dynamics and thermoerosion of shallow
thermokarst ponds on the Northeastern Qinghai–Tibet Plateau, The Cryosphere Discuss., 8, 6117-6146.
Application of SM2RAIN for estimating rainfall from in situ
soil moisture observations
2 HESS Subm.
Beck, H. E., van Dijk, A. I. J. M., Levizzani, V., Schellekens, J., Miralles, D. G., Martens, B., and de Roo, A. (…). MSWEP: 3-hourly 0.25°
global gridded precipitation (1979–2015) by merging gauge, satellite, and reanalysis data. Hydrology and Earth System Sciences
Discussion, in review, doi:10.5194/hess-2016-236.
Independent global scale assessment of SM2RAIN-
ASCAT rainfall product
FOR FURTHER INFORMATION
URL: http://hydrology.irpi.cnr.it/people/l.brocca
URL IRPI: http://hydrology.irpi.cnr.it