Monthly and Seasonal predictions provide information on how averaged conditon of weather is expected comparing to normal over the next few months, e.g. "Are averaged rainfall/temperature over China during the following winter likely to be above or below its climatology?".
The predictions provided on this website are based on the output of BCC’s dynamical climate models. They could be part of the advice to help government agencies and companies with their long-term strategic planning on their own decision-making over a range of time scales.
AGCM (T63L16) and observed SST anomaly persistence are used to conduct ensemble forecast of 45 days for each initial condition. Initial condition of atmosphere comes from the assimilation data of National Meteorological Center, China Meteorological Administration (NMC/CMA) of the latest five days before the first day of each pentad. The persistent anomalies of latest weekly SST are employed as the boundary condition. The prediction includes 40 ensemble members at the utmost. Half of them are generated with lagged-average-forecast (LAF) method, the other half with singular-vector-decomposition (SVD) method.
Products are provided in routine operation way, which include surface temperature, precipitation, sea level pressure, 200hPa, 500hPa, 700hPa geopotential height, 200hPa, 700hPa wind field, as well as re-explanation of numerical forecasts such as temperature and precipitation expressed in terms of three categories: below, near and above normal. The periods of prediction are the coming 1st ten days, 2nd ten days, 3rd ten days, 4th ten days, 1st-30th days and 11th-40th days.
Forecasts are started from observed conditions on the last 8 days of the previous month of issue (month 1) and run forward to a range of 6-months. Forecast maps are provided for three overlapping three-month periods: months 2-4 ahead, months 3-5 ahead and months 4-6 ahead. The Forecast is generated by the BCC-CGCM which consists of T63L16 as AGCM and L30T63 as OGCM coupled with each other in a daily flux correction scheme. There are 48 members for ensemble forecast with 6 oceanic initial conditions provided by BCC-GODAS and 8 atmospheric initial conditions came from the assimilation of NMC/CMA which are the same as in monthly forecast but at 0:00 (GMT) o’clock in last 8 days of previous month of issue.
The WMO-SVSLRF is adopted to verify the forecasts and hindcasts of BCC's model.