Bodo Bookhagen Geography Department, University of California, Santa Barbara ENSO, orographic barriers, and TRMM rainfall along the eastern Andes

Rainfall along the Andes – TRMM2B31 Bookhagen and Strecker, 2008

TRMM platform PR Precipitation Radar TMI TRMM Microwave Imager VRS Visible Infrared Scanner LIS Lightning Image Sensor CERES Cloud and Earth’s Radiant Energy System High-resolution weather parameter measurement between 36°N and 36°S Several instruments on the platform Followed by the GPM (Global Precipitation Measurement) project

Calibration – TRMM2B31 Bookhagen and Strecker, 2008

Calibration of TRMM rainfall Bookhagen and Burbank, in review

Validation – TRMM2B31 and TRMM3B42 TRMM 3B42 – combination of several satellite products scaled to match gauge data Bookhagen and Strecker, 2008

Rainfall variations along the Andes

North and south of 17°S – TRMM2B31 elevation asl (km), mean annual rainfall (m/yr), 3-km-relief (km)

North and south of 17°S – TRMM3B42 elevation asl (km), mean annual rainfall (m/yr), 3-km-relief (km)

North and south of 17°S – relief elevation asl (km), mean annual rainfall (m/yr), 3-km-relief (km)

Rainfall along the Andes – all swaths

Río Pastaza Fitzcarrald arch

Rainfall along the Andes – all swaths

Rainfall along the Andes – relief relation

Santa María Basin, NW Argentina (~27°S)

Relief-Rainfall Relationship Simplified geologic structure of eastern Andes margin north of ~17°S Simplified geologic structure of eastern Andes margin at ~25°S

Rainfall in the Andes knee (orocline)

Impact of ENSO on South America

ENSO oscillations BEST index is a combination of (1) an atmospheric component of the ENSO phenomenon (the Southern Oscillation Index or "SOI") and (2) an oceanic component (Nino 3.4 SST, which is defined as the SST averaged over the region 5N-5S and 170W to 120W), defined by Smith and Sardeshmukh, 2000 Note: No change of pos. or neg. ENSO events if Multivariate ENSO Index is used (MEI)

TRMM 3B42 – mean monthly rainfall 3-hr time intervals achieved through a combination of observations from several satellite platforms (TRMM, SSM/I, AMSR, AMSU) data combined with some ground-station data and gridded to 0.25x0.25° ~30x30km)

Validation – TRMM2B31 and TRMM3B42 TRMM 3B42 – combination of several satellite products scaled to match gauge data Bookhagen and Strecker, 2008

TRMM 3B42 – neg. ENSO

TRMM 3B42 – pos. ENSO

TRMM 3B42 – pos. ENSO anomaly

TRMM 3B42 – neg. ENSO anomaly

TRMM 3B42 – neg. ENSO 3-day anomaly Determining rainfall intensity analyze the timeseries of each pixel separately (>30,000 measurements) by first calculating cumulative rainfall amounts, which integrate rainfall over the previous 1, 2, 3, or 5- day periods (‘smoothing’) Identify mean of each pixel timeseries Count number of events above mean By varying the integration timescale from 1 to 5 days, we take into account the different storm timescales: we observe that the integration over longer time periods (3 or 5 days) limits the relative storm occurrence to the elevated Andes and the Altiplano-Puna Plateau, suggesting that longer lasting storms occur more frequently there.

TRMM 3B42 – neg. ENSO 5-day anomaly

TRMM 3B42 – neg. ENSO 3-day anomaly

TRMM 3B42 – pos. ENSO 3-day anomaly

TRMM 3B42 – no ENSO 3-day anomaly

Drainage Subbasins of the Amazon