Boulder, Oct Challenges in Operational Nowcasting in Beijing Jianjie Wang Beijing Meteorological Bureau, CMA Mingxuan Chen Institute of Urban Meteorology, CMA Oct 24, 2011

Boulder, Oct Impacts of sever weather to Beijing city 1 2 Contents Concluding remarks 3 Performances of existing operational systems (BJ-ANC and BJ-RUC)

Boulder, Oct Impacts of severe weather to Beijing city 1 2 Contents Concluding remarks 3 Performances of existing operational systems (BJ-ANC and BJ-RUC)

Boulder, Oct C 波段（已建） S 波段（在建） C 波段 S Complicated terrain over Beijing Mountainous area is 62% of total territory ( km 2 ) Down town Time series on total numbers of heavy rain (R24h > 50mm) stations in May to Sep during (surface stations + AWS) date Station no.

Boulder, Oct Gust wind Lightning Heavy rain High Urban Density + Large Population + Multi- Transportation Ways+ Rapid Development  Increased Vulnerability to Weather Disasters Due to rapid development of the city, severe weather induced hazards can trigger derivative disasters on the society and the economy of the city. Heavy rain: —— Traffic jam on urban road and highway —— Delay of airplanes and trains —— Water logging in the low-lying places of urban area —— Mud slides in the northwestern mountainous area Hail

Boulder, Oct Eager demands for SW nowcasting from users Requiring accurate & reliable SW nowcasting in terms of:  Weather types (i.e., torrential rain, lightning, hail, gust wind etc)  Starting time and ending time  Specific location  Strength (e.g., hourly rainfall amount, gust wind speed etc)  Lead time (at least 3-6h ahead)  …

Boulder, Oct Impacts of severe weather to Beijing city 1 2 Contents Concluding remarks 3 Performances of existing operational systems (BJ-ANC and BJ-RUC)

Boulder, Oct Data ingest Algorithms Fuzzy logic Dat QC CINRAD radars (4 S-band & 2 C-band), AWS in 5-min, satellites (FY2D/E), rawinsondes, NWP (BJRUC) 3D reflectivity mosaic Storm tracking Reflectivity TRECStorm trend nowcasts Storm reflectivity nowcasts QPE QPF Retrieval of low-level thermo-dynamical fields BJANC: Bei-Jing AutoNowCasting system —developed through the cooperation of BMB and NCAR —be installed in BMB & provincial weather offices of northern China

Boulder, Oct Used radars: Beijing S-band (BJRS) Tianjin S-band (TJRS) Shijiazhuang S-band (SJZRS) Qinhuangdao S-band (QHDRS) – added since B08 Zhangbei C-band (ZBRC) Chengde C-band (CDRC) – added since B08 B08: 500km×500km Now: 700km×700km BJANC domain

Boulder, Oct Statistic verification on 0-1h forecasts of QPF,and storm cell tracking from BJANC ( summertime averaged)

Boulder, Oct :0015:0018:0021:0000:0003:0006:0009:00 Cold start, 24h forecast Warm start, 24h or 36h forecast 12:0015:0018:0021:0000:0003:0006:0009:00 Initiation (UTC) 3DVAR assimilation (UTC) rawinsondes, surface OBS, ship/buoy, AWS, AMDAR, ground based GPS_MET BJRUC: Bei-Jing Rupid Updating Cycle system —Developed on the basis of WRF model system D1 D3 D1 D2 D3 3km, 37 level, Ptop=50hPa

Boulder, Oct SYNOP AMDAR SOUND SHIP&BUOY Data assimilated by BJ-RUC AWS Ground-based GPS

Boulder, Oct Point verification on R1h forecasts within 24h range (15 surface stations, data of 2008/06/ /05/31, referenced from Wei Dong etc.) (a) Valid at the same time Valid not at the same time but at the same time range

Boulder, Oct Sounding/12h Analysis fields/6h Surface OBS/3h Global NWP guidance/12h BJRUC guidance/3h AWS OBS/5min Radar OBS/6min Wind profile/6min BJANC guidance/6min Lightning detection Satellite OBS/30min 24-12h 6h SW starting0h Warning issuing Forecast on SW potential BJT times in daily weather forecast issuing Data support for SW forecast issuing

Boulder, Oct DateAve. Rainfall (mm) Max. of R1h (mm) CoverageLasting (hour) Synoptic forcing July Whole area16Strong July Partial area6Weak July Whole area19Strong Aug Partial area7Weak Aug Partial area6Weak Aug Whole area20Strong Investigation from forecaster’s perspective (all cases in late July to early Aug of 2011 with R1h max >50mm)

Boulder, Oct Lasting 16h 83.7mm/h Lasting 6h 80.2mm/h Under strong synoptic forcing Under weak synoptic forcing

Boulder, Oct Look into meso-scale features Under strong synoptic forcing; Longer lasting Under weak synoptic forcing; Short lived R1h, R3h features (time, shape, distribution, amount, movement), cells BJRUC (0-24h) 8 runs in a day- cycle, and targeting whole raining period R1h features, cell formation, evolution and reflectivity BJANC (0-2h) Every 6 min, and targeting whole raining period

Boulder, Oct Under strong synoptic forcing The meso-  spatial and temporal features of 1~ 3h accumulated precipitation over Beijing area could be captured reasonably well within 24h. QPF products valid at the same time from cycled runs within 24h period provide generally consistent information in terms of the raining time, rainfall location, amount and movement etc. “spin up” effect has clear impacts to the “cold start” run of the BJRUC. BJRUC Results-1

Boulder, Oct Initiation: 2011/08/14 08:00 (12-15h) Initiation: 2011/08/14 14:00 (6-9h) Initiation: 2011/08/14 20:00 (0-3h) 2011/08/14 20:00-23:00 From the cold start run R3h of OBS versus that of BJRUC

Boulder, Oct Under weak synoptic forcing There are visible bias on QPF products generally. The information of QPF products from cycled runs valid at the same time tends to diverse run to run. BJRUC could predict quite well the torrential rain induced by short-lived convections, occasionally, when signals of the local convective potential had occurred in model initial time and was captured by the model properly. BJRUC Results-2

Boulder, Oct /08/09 OBS 15:00-16:0016:00-17:0017:00-18:0018:00-19:0019:00-20:00 Initiation: 2011/08/08 20:00 Initiation: 2011/08/09 08:00 20h 12h 10h8h 22h24h

Boulder, Oct :00-00:0000:00-01:0001:00-02:0002:00-03:0003:00-04: /08/14 OBS Initiation: 2011/08/13 14:00 11h 12h 13h14h

Boulder, Oct /08/13 14:00 (Initiation time) 2011/08/13 20:00 (3h ahead rain) Initiation: (6h) 2011/08/13 14:00 KSICAPELCL OBS 14: OBS 20: BJRUC 20:

Boulder, Oct /08/13 23:00 BJT 2011/08/14 00:00 BJT 2011/08/14 01:00 BJT 2011/08/14 02:00 BJT 2011/08/14 03:00 BJT2011/08/14 04:00 BJT BJRUC Initiation: 2011/08/13 14:00 BJT 9h10h 12h13h 11h 14h

Boulder, Oct h nowcasting products (the track, trend, reflectivity and quantitative precipitation etc) are precise and reliable generally. Although the nowcasting skill reduces with forecast valid time, 2h nowcasting is still quite valuable under strong synoptic forcing. Because of the quick update (in 6 min) on radar data, the bias of nowcasting products could be adjusted fast by the system itself so that make less impacts to the proper use of the products in operation in general. BJANC Results-1

Boulder, Oct /08/14 01:59 BJT2011/08/14 02:59 BJT 2011/08/14 02:00-03:00 1h rain OBS 2011/08/14 01:59 BJT 1h rain nowcast valid at 2011/08/14 02: /08/14 00:59 BJT After 1h After 2h After 1h

Boulder, Oct Limitations on Identification of the initiation of convective cells Proper prediction on the track/trend/QPF of new cells in their very early development stage (about 0-18min after initiation) Reasonable prediction on cell-evolution in the mountainous and transitional areas BJANC Results-2

Boulder, Oct /07/26 21:06 21:18 21:24 21:30 Rapid development Rainfall rate Max 10.2mm/5min

Boulder, Oct /07/26 21:12 BJT Cell identification 2011/07/26 21:06 BJT Cell formation 2011/07/26 21:06 BJT Beginning stage With limitation on identifying & predicting new cells 2011/07/26 21:24 BJT Correct nowcasting 30min trend 30min rainfall noecast Bias in early stage but adjusted quickly

Boulder, Oct With difficult on predicting cell evolution down to the mountain 2011/08/09 15:36 BJT Bias on track 2011/08/09 16:00 BJT Down to the mountain 2011/08/09 16:06 BJT formation of new cell 2011/08/09 16:18 BJT Bias on track 2011/08/09 16:36 BJT Correct track 2011/08/09 17:36 BJT Verification on cell merging

Boulder, Oct Impacts of sever weather to Beijing city 1 2 Contents Concluding remarks 3 Performances of existing operational systems (BJ-ANC and BJ-RUC)

Boulder, Oct GapsIn SW warningIn objective techniques (BJRUC, BJANC) In capacity of forecasters Items SW type (hail, gust wind) nowcasting without or lack of objective guidance Early issuing of SW warning (6h ahead) lack of reliable objective guidance Inconsistency of BJRUC guidance run to run, mainly under weak synoptic forcing, caused by: deficient initial condition “spin up” in cold start run Limitation on BJANC nowcasting new cell formation and its very early development cell evolution over complex terrain Limited knowledge and experiences on the new tech: objective nowcast / forecast techniques remote sensing data Limited knowledge on the mechanism of convection Steps Hybrid approach: (objective methods + high resolution OBS + forecaster’s knowledge & experiences on SW) Improving the objective methods Developing new techniques (pay more attention to the causes behind in weak synoptic forcing situation) Training to forecasters Investigation on SW & performance of BJANC, BJRUC … Main gaps in operational nowcasting in BMB

Boulder, Oct Future Development Blending (BJANC and BJRUC) on QPF Improvement of BJRUC’s initial condition (radar data assimilation, initialization scheme, etc.) Improvement of BJANC’s key algorithms on identifying new cells and forecasting storm quick evolution (combining forecaster’s experiences) Radar QC Product generation (VDRAS, SW type based on conceptual model, interpretation to BJRUC guidance, etc.)

Boulder, Oct Acknowledgement Thanks to my colleagues for their support to this investigation: Min Chen Chenyun Sun Guorong Wang Xiaoqing Ma Jisong Sun et al.

Boulder, Oct Thanks!