South Asian Climate Outlook Forum (SASCOF-5) 14 th -25 th April,2014,IMD,Pune, India Chhimi Wangda Department of Hydrometeorology Services, Thimphu,Bhutan.

Over View Country introduction Climate of Bhutan Monsoon in Bhutan Operational weather forecasting system Seasonal outlook for Bhutan

Facts of Bhutan Location: Southern Asia, between China & India Total area: 38,394 Sq. Km Population : 750, % of population is farmer Forest Coverage: 72.5% - Policy is to ensure at least 60% for all time Topography : 95% Mountain terrain Coordinates: 27.41N,90.40E China Bhutan

Climate of Bhutan Varies within different zones Tropical climate in the southern foothills-hot and humid and the seasonal variation is dominated by precipitation. Cool winter and hot summer in central valleys; Severe winters and cool summers in the Himalayas

Climatic Zones of Bhutan Sub – Tropical Zone Temperate Zone Sub Alpine Zone Alpine Zone Elevation: Lowest 97 m (318 ft) to 7,570 m (24,836 ft)

Sub – Tropical Zone Ranges 200m to 2000 meters above sea level. Winter mean temperature is about 15 Degree C Summer mean temperature is about 28 Degree C The total annual rain fall is usually above 2000mm.

The Temperate Zone Ranges 2000m to 3000 meters above sea level. Winter mean temperature varies from 5°C to 8°C. Summer mean temperature varies 10°C to 22°C. The total annual rain fall varies from 1500mm to 2000mm.

Background of DHMS 2011 – Full-fledged department 2007 – Weather forecast initiated Until then- Functioned as meteorological data collector Mandates and responsibilities increased And user demand for climate services has increased

Organogram of DHMS Director Department of Hydro Met Services Planning, Coordination & Research Division Meteorology Division (MD) Hydrology Division (HD) Snow and Glacier Division Operation & Maintenance Section Agro met/Climatology SectionAviation Meteorology Section Construction & Instrumentation Unit Weather Forecasting Unit Regional Meteorological Stations Data Processing Unit

10 SOUTH EAST MONSOON (October to March) ‏ NORTH WEST MONSOON (June to September) ‏ BHUTAN SUMMER MONSOONWINTER MONSOON Monsoon in Bhutan Climatic condition is generally dominated by monsoon winds with dry winter and wet summer monsoon Premonsoon- MAM, Post monsoon-SON

Monsoon seasons in Bhutan JJAS

Rainfall distribution pattern Stations Altitude in meters Rainfall in mm Deothang Bhur P/ling Samtse Pemagatshel Zemgang Tsirang Dagana Chukha Tashigang Mongar Bhumthang Wangdi Punakha Thimphu Paro Haa Trashiyangtse Lhuentse  More rainfall in southern and central part –more settlements

Rain varies with altitude Southern foothills vulnerable to monsoon related disaster Foothills = Fragile and prone to landslides Mid Himalayan rain variation = local effects?? Or location of met station?  Rain 1.7 mm decline per meter rise in altitude  Correlation ® =  Well defined R squared = 0.64  Statistically significant influence of altitude for rainfall distribution  Lowest rain in Thimphu

Common Natural Disasters in Bhutan Flood GLOF Flashfloods Landslides- Huge govt. expenditure Wind storm – pre monsoon Thunder storm Epidemics, pests and diseases: Earthquakes Forest Fires Weather & Climate related

Extreme weather events in 2013 Monthly Rain pattern in Bhutan  Rainy Season from JJAS (Monsoon)  Dry Winter (NDJF)  Natural disaster occurs in Monsoon

Rainfall % deviation  2013 June rainfall below normal  Persistence below normal rain in June from 2005 – (Drought???)

Rainfall departure-( )  Rainfall 1 – 26 July below normal

Operational Weather Forecast in DHMS Weather forecast has been a very tough job in Bhutan Depend on regional products for weather forecast Meteogram Temperature mean Temperature (Max & Min) mean Observation Temperature (Max & Min) from Class A station. Real Time Data (Temperature) validation

Operational Weather Forecast in DHMS Some of the readily available references Website Indian Met Dept Thai Met Dept Models Satellite

Operational Weather Forecast in DHMS Satellite Images Near real time observation Clouds formation and types Level of clouds Wind speed & direction at different levels Cold body and warm body

Operational Weather Forecast in DHMS- Model output MetGIS

Meteorological station network

Long Range Forecast( LRF) in DHMS Experimental-First attempt to prepare seasonal forecast began in 2013 LRF seasonal forecast issued in May 2013 with the help of regional expertise and available sources( IMD,SMRC,KMD) Constrained by professionals and lack of LRF office

2013 monsoon outlook Used CPT for the preparation of outlook Observed average rainfall data since and ERSST data as predictor Coverage area of ERSST data used as predictors:  Pacific ocean region  IOD region  Indian Ocean region  Bay of Bengal

Bhutan monsoon outlook 2013 Normal to slightly normal Moonsoon onset forecast – 6 th June Forecast was not good

South West Monsoon Outlook JJAS 2014 SST indices used as predictors: SSTv3 (March) 2. SSTv3 (Nov-Dec) 3. MSLP(Feb) 4. WWv anomaly( Feb and Mar)

Predictand: Average RF data JJAS CCA run CPT Goodness index=0.16

CCA maps (CC)=0.54

Correlations

Probabilistic forecast values Index-JJAS Below= 61%:Normal-25%;Above-14%

Multi model probabilistic ensemble forecast

Summary The CCA model out put of CPT indicate below normal rainfall for JJAS but the validation with other models with different predictors such as SST is required to improve the final forecast of monsoon rainfall over Bhutan.

Thank you