Application of Real-Time Extended-Range Forecast Products from a Spatial-Temporal Projection Model

Chongbo Zhao*, Lijuan Chen, Hong-Li Ren, Jie Wu, Tim Li, Pang-chi Hsu, Zhiwei ZhuLaboratory for Climate Studies, National Climate Center, China Meteorological Administration, Beijing 100081, China. * zhaochongbo@cma.gov.cn

Abstract Based on a non-filter method to extract intraseasonal signal designed by Hsu et al. and a spatial-temporal

projection model to provide forecast products for the next 6 pentads established by Zhu et al., an MJO monitoring and

prediction operation system was built up in National Climate Center (NCC), and real-time products were carried out

and updated daily on the website (http://cmdp.ncc-cma.net/Monitoring/moni_mjo.php). Through the impact of

equatorial MJO activity on NAO, ENSO, summer monsoon onset in the South China Sea, and the typhoon activity

over Northwest Pacific, the prediction of MJO can provide a reference for a variety of climatic phenomena forecast.

Since the direct effect of MJO on the precipitation and temperature in China is limited to the south China, this

operation system also provides real-time extended-range prediction products of precipitation and temperature at 723

stations over China. The current statistical model shows encouraging ability.

1. Background of Extended-Range Forecast

Based on a spatial-temporal projection model, an MJO monitoring and prediction operation system was built up in NCC, and

real-time products were carried out and updated daily on the website (http://cmdp.ncc-cma.net/Monitoring/moni_mjo.php).

Through the relationship between MJO and El nino, NAO, summer monsoon onset in the South China Sea, and typhoon

activity over Northwest Pacific, MJO prediction can provide a reference for a variety of climatic phenomena forecast. Since the

direct effect of MJO on the precipitation and temperature in China is limited, this model is re-builted to forecast real-time

extended-range prediction products of precipitation and temperature at 723 stations over China. The current statistical model

shows encouraging ability.

4. Summary

MJO also has a modulation effect on the typhoon. From the end of June last

year, three Northwest Pacific typhoons (No. 9 "Chan-Hom“, No. 10 "Lotus“,

No. 11 "Nangka") have generated, forming a situation of "three typhoons

dance together". Previouse study shows the MJO convection over WP favor

the typhoon generation. In 5d to 20-day-lead forecast, the MJO located in the

phase 6 and 7 at the end of June, which is conducive to the generation.

Therefore, through the relationship between the MJO phase and the typhoon

generation, the forecasted MJO phase can give some guidance to the typhoon

generation condition.

In recent, the spatial-temporal projection method (STPM) can extend

the valid length of the MJO prediction to 25-30 days in terms of

pentad mean (Zhu et al. 2015). The major steps for constructing the

STPM is use every preceding 6 pentads Predictor before forecast time

as left field and succeeding 6 pentads Predictand as right filed. Based

on extended-SVD during 1979-2001, the main coupled evolution

patterns is obtained. When we do the realtime forecast, first Project

the 6 pentads realtime predictor fields onto left ESVD modes, then use

the time coefficient dot-multiply right modes, The re-construction of

the forecast field is obtained. Finally multiply a ratio between standard

deviations of observed and reconstructed predictand fields during

1979-2001, The actual forecast field is obtained. This model is already

being test used for realtime prediction in BCC and the products are

updated daily on the website (http://cmdp.ncc-cma.net/

Monitoring/mo ni_mjo.php). The real-time products include recent

evolution and prediction of the zonal wind and OLR anomaly time-

longitude section and RMM index.

2. MJO Prediction based on STPM

Given the importance of extended-range forecast on agricultural

management and the disaster prevention and reduction, the

government and the public have the increasing needs for such

information. For example, due to the cold rain and snow in South

China during January in 2008, a lot of cars are stuck on the

highway.

Severe drought in the southwest of China during the winter of 2009

and many heavy rainfall processes in South China this summer put

forward the urgent need of a better service production for the

extended range forecast.

Dynamic model is the main tool for Extended Range Forecast.

However, In the extended range period, the information of the

initial state is gradually dissipated with the forecast time, but the

role of the external forcing is not completely dominant. Therefore,

the numerical forecast skill in the extended period is poor and the

extended-range forecast became an “operational forecast gap”,

which can not meet the service needs.

Fig.2 Brief introduction of Extended-Range Forecast

(ERF)

In view of the high frequency of making extended-

range forecast production, the statistical model seems

more efficient. An important predictability source of

extended-range forecast is Madden–Julian Oscillation

(MJO) and it has notable global impact. MJO is the

dominant mode of the sub seasonal to seasonal (S2S)

time scale variability. It has great impacts on weather

and climate events at low latitudes, and also influences

the circulation at mid high latitudes, which presents a

primary source of predictability on extended range time

scale. The spatial-temporal projection method (STPM)

model is first used into MJO prediction.

Fig.6 A Monitor and Forecast Case of U850 in last year

<- Fig.8 Daily NAO index (red), MJO phase monitor (black), and forecasted

MJO phase of 5-30 days leading time (lower panels) from 20071023 to

20080420

The impact of MJO on South China Sea summer monsoon onset shows that

MJO in phase 4, 5, 6, 7 is favorable to the onset of SCS summer monsoon due

to an anomalous cyclonic circulation at low level over SCS as Rossby wave

respond. MJO in phase 8, 1, 2, 3 is unfavorable to the onset. For example, The

SCS summer monsoon in 2004 bursted out on May 9th, which is 2 days earlier

than the mean onset date. Therefore, through the relationship between the MJO

phase and the SCS summer monsoon onset, the forecasted MJO phase diagram

can give guidance to the SCS summer monsoon onset condition.

Fig.9 The observed (solid) and

predicted (right) phase diagrams of

RMM (dashed) in April and May during

2004 (left) and 2006(right) ->

Fig.11 Regression coefficient (color) and correlation coefficient (dot means

coefficient exceed 95% confidence level) of precipitation and RMM index

during 1979-2015.

Fig.1 Photos of disasters caused by the freezing

rain，drought，and extreme rainfall events

3. Application of Real-Time Extended-Range MJO Prediction

OLR and the zonal wind are typical variables to describe the MJO. In addition to these three variables, according to the

analysis, the lower troposphere moisture convergence ahead MJO convection is important in MJO initiation, This leading

structure also exist during the MJO eastward propagating (Li et al., 2015; Hsu et al., 2012), Therefore, low-level relative

humidity and divergence and Geopotential Height are selected for statistical modeling. The predictor include OLR, U200,

U850, R700, D850, H200, H500, H850.

Many studies show that 10 days after MJO phase 3 the North Atlantic

Oscillation (NAO) is in positive phase. During winter of 2007, there are

3 MJO events, 10 days after every phase 3, the daily NAO index is

positive. The forecasted MJO phase is consist with the observation, and

this has an indication of how the future nao index will be.

Fig.12 The real-time products include

anomalous precipitation and temperature

prediction of next 6 pantads (http://cmdp.

ncc-cma.net/pred/cn_s2s.php)

Besides the climate system above, the

precipitation and the temperature in China

are still the most important we care about.

In Fig. 11, the correlation coefficient

(black dot0 between precipitation and

RMM index shows that the direct effect

of MJO on station precipitation is limited

to South China. Therefore, to meet the

needs of prediction service, taking

precipitation as forecast object to build

model is necessary. When using STPM

taking summer precipitation as predictand

derectly. There are significant correlation

coefficient. Even in the 30-day-lead

forecast, the forecast skills in the

southeast of Tibet, Guangxi province, the

middle and lower Yangtze River still

exceed 95% confidence level. Also taking

winter temperature as predictand derectly,

the skill is much higher than precipitation,

In the 30-day-lead forecast, except for the

surrounding areas of Tibet Plateau and

southwest region, the forecast skills still

is very high.

Extended Range Forecast

Fig.4 Methodological diagram of the

STPM

(Hsu et al., 2015; Zhu et al., 2015)

MJO Initiation MJO Propagation

Fig.3 Lower-troposphere moisture convergence ahead MJO convection during its initiation and eastward

propagation.

Fig.5 The real-

time products

include recent

evolution and

prediction of

the zonal wind

and OLR

anomaly time-

longitude

section and

RMM index.

(http://cmdp.nc

c-cma.net/

Monitoring/mo

ni_mjo.php)

When we get the future MJO, then what

purpose can it serve? This is a Monitor and

Forecast Case in last year (Fig. 6). From March,

westerly anomalies propagated eastward,

meanwhile the El Niño type changed from

Central-Pacific to Eastern-Pacific (Fig. 7), the

forecasted new westerly events consistent with

the observation, and eastern Pacific Nino index

increase further.

Fig.7 Monitor Nino indices for the El Niño

type of Eastern-Pacific and Central-Pacific

Fig.10 The observed (solid) and predicted

(right) phase diagrams of RMM (dashed)

from June to July during last year

early late