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Context: In Jan 2011 FEWS NET issued an accurate projection of food insecurity if the long rains failed, how predictable might the long rains be?. This study analyzes January and MAM climate fields for 8 recent drought years. Outlier.

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slide1
Context: In Jan 2011 FEWS NET issuedan accurate projection of food insecurity if the long rains failed, how predictable might the long rains be?
this study analyzes january and mam climate fields for 8 recent drought years
This study analyzes January and MAM climate fields for 8 recent drought years

Outlier

MAM SPI time-series for high-risk region in southern Ethiopia, central-eastern Kenya and Southern Somalia. Boxes show drought years (those with SPI <-0.5). While 1992 was an outlier, all the other years exhibited similar SST gradients, and large scale atmospheric responses. Data: GPCP topped with RFE2 for 2011

merra mam sst z scores
MERRA MAM SST Z-scores

Brown = Hot

Blue =Cold

While the positions vary, in all dry seasons, an SST gradient existed across the western-central Pacific. The role of the Indian Ocean is less clear. MAM climate seems similar to January climate in the Pacific, supporting prediction.

slide4
1984

Wet

Wet

Warm

slide5
2000

Wet

Wet

Warm

slide6
2004

Warm

Wet

Wet

2004 seems more influenced by Indian Ocean Dipole

slide7
2007

Wet

Wet

Warm

slide8
2008

Wet

Wet

Warm

slide9
2009

Wet

Wet

Warm

slide10
2011

Warm

Wet

Wet

wet dry and normal year sst transects
Wet, Dry and Normal Year SST transects

Key Points : 1) Note that SST relationship across the Pac is uncorrelated, wet and dry years cool!

2) Nonetheless, 7 of 8 dry years have SST gradient

3) Even with low grid cell correlations, the GFS might capture the impact of the SST gradients

coherent patterns excluding 1992
Coherent patterns (Excluding 1992)
  • Western and Central Pacific SST gradients appear to be the key forcing element
    • SST z-scores exhibit a steep down-up-down pattern, with a maxima between 140°E and 160°E
    • These gradients represent substantial zonal available potential energy
  • All years exhibited a rainfall gradient maxima to the west of the SST gradient maxima (between 80 and 120E)
  • All years exhibited large easterly moisture transport anomalies across the eastern Pacific, and some westerly transport anomalies into the western Pacific
  • The large scale climate anomalies are large (quasi-global?), and likely to be persistent, and predictive
  • The SST-gradient driven anomalous circulation patterns are likely to be predicted well using climate models driven with SSTs.
    • Statistical modeling seems difficult, given the spatial non-stationarity
    • Coupled models seem to have weak Western Pacific rainfall responses, and hence may not be the best predictive tool
merra mam precip
MERRA MAM Precip

Brown = Dry

Blue = Wet

slide17
Modeling Experiment
  • Multi-model ensemble mean (72 members) MAM RR anomaly (mm/day) from simulations using observed SSTs, averaged over1999-2009.
  • Ensemble mean (24 members) ECHAM5 precipitation anomaly (mm/day) from idealized runs forced with observed March-May SST anomalies averaged over 1999-2010 for the tropical Indian Ocean only.
  • As in b, but for model runs forced with SSTs only for the tropical Pacific. Top legend only for a); bottom legend for b and c.

SST Anomalies used to drive the model

Side shows research by Bradfield Lyon (IRI) presented by TufaDinku (IRI) at the CRAM3

cca forecast ssts
CCA(Forecast SSTs)

Figure x. Relative forecast probabilities of below normal rainfall, based on ECHAM4.5 and CCM3.6 models driven with forecast

sea surface temperatures. The probability of below normal rainfall in 2012 appears broadly similar to these analog years.

Analysis provided by Bradfield Lyon, International Research Institute for Climate and Society.

sst based analog analysis
SST based Analog Analysis

Pacific and Indian Ocean SST indices.

slide24
Analog years analysis for April & May

Chris Funk: 2000, 2008 & 2011

KMD: 2001 & 2009

Key messages:

Consistent observations of increased likelihood for poor rainfall performance over northern and central Tanzania, southern, central, eastern and northern Kenya, together with Somali and Afar regions of Ethiopia (<75% of normal) .

Emerging areas of concern in Rwanda and Burundi during the months of April and May, with mixed rainfall performance likely in south and central Somalia.

slide25
Analog years analysis for Maize WRSI/EoS

2011

2008

2000

Key messages:

Increased likelihood (80% chance ) for crop failure in SE and coastal strip of Kenya, S. Somalia and N. Tanzania.

100% likelihood for near normal cropping conditions for key agric areas of Kenya and Uganda.

About 60% likelihood for normal cropping conditions in Rwanda and Burundi.

Mixed crop performance for Meher/Belg cropping areas despite delayed onset(?)

2001

2009

slide26
Analog years analysis for Rangelands WRSI/EoS

2011

2008

2000

2001

2009

Key messages:

Mixed performance in rangeland conditions in the region, due to expected poor rainfall distribution in space and time over the key pastoral areas.

Increased likelihood for poor rangeland conditions over N. and S. Kenya, Somali region of Ethiopia and parts of Somaliland, Djibouti and S. Eritrea.

proposed climate projection forecast system
Proposed Climate Projection/Forecast System

Winds

Rainfall

Temperature

Observed & predicted SSTs

Climate Models

Hoerling/Hurrel Decadal SST predictions

PET z

ObsRainfallTS

CA

CCA

MFR ...

T z

PETobsm,s

Additional (Filtered CMIP5)SST predictions

GHGs

Tobsm,s

FutureRainfallTS

Probs

Future

TempTS

Probs

Future

PETTS

Probs

SPI

FLDAS

WRSI

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