The purpose of this module is to introduce the forecast products currently available in
Bangladesh and explain their utility for improving the adaptive capacity of rural livelihoods
to climate risks. Upon completion of this module, participants should be able to:
■ describe the various types of forecast products available in Bangladesh,
■ elaborate how current forecast products may be used for drought risk
management in agriculture and allied sectors, and
■ understand rainfall forecasts and their use in decision-making
Improved climate information and prediction is one of the most important elements of
adaptation. Adaptation requires working in multiple time scales, from short term to the very long
term, addressing climate variability and change through a range of forecasting systems to add
incremental value to the entire adaptation process.
Climate change models possess inherent uncertainties.
Thus, generating locally usable climate change
information in drought-prone areas requires additional
considerations. There will be a need to incorporate short-,
medium- and long-lead climate forecast information
products in order to develop location-specific impact
outlooks and agricultural response options.
Forecasting weather refers to the likely behaviour of the
atmosphere in advance or foretelling the likely status of
the atmosphere in relation to various weather parameters
such as rainfall, temperature or wind. Generally, forecasts involving weather and climate are
divided into three major types based on their lead-time: short range, medium range and
long range.
Short-range forecasts, covering a period of 24 to 72 hours, are based on atmospheric circulation
patterns that are monitored by satellites and synoptic observatories. Their accuracy is high, as
they cover only a few days. This method is used to forecast cyclones, associated wind speed and
temperature and is useful for timing decisions on sowing/planting, harvesting, fertilizer
application and post-harvest operations.
Medium-range forecasts, covering a period of three to ten days, are based on numerical weather
prediction models (mathematical formulae) that explain physical atmospheric processes. This
method can provide information about rainfall, wind speed, wind direction, cloud cover and
temperature and, on occasion, can extend forecasting to 25 or 30 days. This type of forecasting
is useful for timing decisions on such activities as sowing/planting, irrigation or harvesting.
MODULE 6
Climate forecast application to
improve adaptive capacity
Box 6.1: Weather and Climate forecasting
Weather forecasts predict the behaviour of the
atmosphere over the course of a few days.
Climate forecasting looks at the likely patterns of
climate variables such as rainfall and temperature for
longer periods (months or seasons) with sufficient
lead-time (before the start of the season).
48CLIMATE VARIABILITY AND CHANGE: ADAPTATION TO DROUGHT IN BANGLADESH
Long-range forecasts, covering a period of a month up to a season or more, are generated using
statistical relationships between rainfall and various atmospheric and oceanic variables. Currently,
General Circulation Models (GCMs) are used for seasonal or long-range forecasting which is also
referred to as climate forecasting or seasonal climate forecasting. Seasonal climate forecast maps
are usually qualitative, indicating probability of wetter/drier than normal conditions. Such
seasonal forecasts, including analog and climatology forecasts, are adequate for understanding
general trends. The long-range forecasts are highly useful for drought risk management in
agriculture. The long-range forecasts support decisions on such matters as choice of
crop/cropping systems, selection of crop varieties and resource allocation.
Weather and climate forecasts in Bangladesh
The Bangladesh Meteorological Department (BMD), under the Ministry of Defense, provides
relevant weather forecasts on a regular basis. It operates 35 meteorological stations throughout
the country, of which ten provide agro-meteorological data, reporting daily to the central office
in Dhaka. The BMD Storm Warning Centre (SWC) issues daily forecasts based on analysis of
meteorological charts and satellite and radar images.
Special bulletins on drought
In addition to routine daily forecasts, BMD issues special weather bulletins for heavy rainfall,
droughts, tropical cyclones and associated storm surges. In addition, it issues one-month
forecasts for the general public and authorities and long-term agro-meteorological forecasts
valid for three months (updated every month). Medium-range, 10-day agro-meteorological
advisories are also issued.
Observation network
In the above forecasts, meteorological observations are used as basic input. BMD has a
meteorological observation network throughout the country consisting of 35 surface
observatories recording observations eight times a day. Ten Pilot Balloon Observatories record
upper wind direction and speed four times a day, three Radiosonde Stations record upper-air
wind, temperature, humidity and pressure twice a day. The BMD also operates 10 agrometeorological
stations.
The Agro-meteorological Division of BMD issues a bulletin every ten days with meteorological
data from 32 meteorological stations, highlights the rainfall situation and offers 10-day forecasts.
The Department of Agricultural Extension (DAE) operates 64 rainfall stations, one at each
district agricultural office. Daily rainfall data is compiled by the BMD Deputy Director’s office
and communicated to the DAE in Dhaka.
Application of climate forecasts
The effective use of climate forecasts requires that:
■ the right audience receives and correctly interprets the right information at the right time,
■ the information is relevant to decisions concerning drought risk reduction, and
■ the forecast information is supplemented with impact outlooks and a drought
management plan.
The criteria for effective communication of climate forecasts are:
■ forecast products should contain relevant information that is important to the user
community (local extension officers and farmers),
■ a probabilistic forecast should accompany information on the possible impact of
drought and risk management measures.
49
module 6
Preparation of drought risk and management plan matrix
The adaptation options to climate change require appropriate use of climate information.
Achieving potential crop yield requires increased resource management through appropriate
use of climate information. It is essential to identify the key drought risks during the crop growth
cycle and the management alternatives.
Drought during the monsoon as well as in the dry season is very common due to the high level
of rainfall variability. Aus rice is affected by early drought or the false start of monsoon rains
with breaks at the beginning that cause poor crop establishment. The aus and t.aman crops are
constantly affected by mid-season and terminal drought in the high Barind tracts. In medium
highlands, t.aman is affected by late season drought during October and November. Adjusting
the time of transplanting of t.aman, based on climate forecast information, can reduce the
impacts of drought. Alternative options would be to select drought-tolerant varieties.