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Flooding in Pakistan caused by higher-than-normal monsoon rainfall

TRMM real-time data indicates extraordinary flooding is related to unusually heavy monsoon rains

Flooding in Pakistan caused by higher-than-normal monsoon rainfall

Landsat 5 image of Indus River flooding near Hyderabad, Pakistan

Flooding in Pakistan caused by higher-than-normal monsoon rainfall

During the months of July and August 2010, considerably higher than normal monsoon precipitation fell in Pakistan.   The upstream areas of the Indus River basin were particularly affected by the inundating rains.   Massive flooding has occurred in the Indus River basin, leaving millions of people homeless and dependent on aid shipments for sustenance.   Numerous roads and bridges have been washed away, accentuating the difficulty of reaching the affected population.  According to news reports, over 2000 people have perished and about 20 million people were rendered homeless.

The Earth Observatory Image of the Day for August 24, 2010, which is the source of the image at right, shows the extent of flooding along the river.   Go to this Image of the Day, "Flooding in Pakistan", to view the full Landsat-5 image.

 

An analysis of TRMM TMPA-RT data indicates that rainfall in Pakistan and the Indus River basin is not unusual in July and August, as this is the Arabian Sea monsoon season.   This year, however, the monsoon rainfall in Pakistan has been unusually persistent and much higher than the same period of time in the previous year (2009).  

Figure 1 (below left) is an image of Pakistan, showing the prominent Indus River valley, acquired by the Moderate Resolution Imaging Spectro-radiometer (MODIS).   Figure 2 (below right) is an animation derived  from the Global Merged IR data set, showing the development of large storms over central Pakistan on July 12, 2010.

 modis image of pakistan and indus river (jpeg)     animation of monsoon storms over pakistan, mid-july 2010

Figure 1 (left):  MODIS image of Pakistan and the Indus River valley.   The Arabian Sea is at lower left, and the Karakoram range of the Himalaya mountains is at upper right.  The whitish area on the India-Pakistan border at bottom center is the Rann of Kutch salt marshes.  (Link to original image at NASA Visible Earth) 

Figure 2 (right):   Global merged IR animation at 1-hour intervals on July 12, 2010, showing development of heavy rainstorms over central Pakistan.

The Giovanni-generated images below (Figure 3) show a comparison of the rainfall amounts for the period July 1 - August 23, in the years 2009 and 2010.    This comparison shows that the monsoon rains in 2010 were heavier and covered a much larger area than for the same period of time in 2009.

trmm tmpa-rt rainfall accumulation comparison, 2009 and 2010, for pakistan floods

Figure 3:    Comparison of rainfall for the period July 1-August 23 in 2009 (top) and 2010 (bottom) for Pakistan and adjacent countries.   Overall monsoon rainfall for the entire region (including northern India) is higher for 2010 than 2009, and the total area in Pakistan receiving monsoon rain is much larger.

The TRMM TMPA-RT time-series comparison generated by Giovanni shown below (Figure 4) provides a clear visual statement of the difference in monsoon rainfall intensity in central Pakistan for the July-August period in 2009 and 2010.    In 2010, there are several large rainfall events – some of which delivered twice as much rain as the largest monsoon rainfall events in 2009.   So this tragic flooding event is one apparently due to intensification of the water cycle – a common pattern seen in climate modeling as global temperatures increase – causing an increase in atmospheric humidity and precipitation.

 

trmm tmpa-rt 2009 and 2010 rainfall time-series comparison

Figure 4:   Time-series comparison of rainfall for central Pakistan in 2009 (top) and 2010 (bottom).  These time-series clearly show that the accumulated rainfall from monsoon rains in 2010 considerably exceeded the accumulated rainfall from monsoon rains in 2009.   Taken together, the larger areal extent and higher accumulation totals indicate that the flooding in Pakistan was caused by unusually strong monsoon rainfall.

 

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Last updated: Dec 14, 2010 02:00 PM ET