Paper 1: UHI from Beijing

1. Paper 1: UHI from Beijing Research Method • Jin, S. M. 2012: Developing an Index to Measure Urban Heat Island Effect Using Satellite Land Skin Temperature and Land Cover Observations. J. of Climate, vol 25, 6193-6201.

2. Urban Heat Island Effect (UHI) This phenomenon describes urban and suburban temperatures that are 2 to 10°F (1 to 6°C) hotter than nearby rural areas. Because all the terms in the surface energy balance are changed in urban regions. (1-α)Sd +LWd-εσTskin4 –SH-LE - G= 0

3. What is the problem? INTRODUCTIONSection: • What is the Approach • What is the New Finding’s contribution to UHI research?

4. MODIS Observation Beijing

6. Urbanization changes surface albedo (MODIS) (Jin, Dickinson, and Zhang 2005, J. of Climate)

7. Urbanization changes surface emissivity (MODIS)

8. a. b. c. d.

9. Figure 3: Monthly mean skin temperature in July 2008 for Beijing observed by Terra daytime (10:30AM), Aqua Daytime (1:30 PM), Terra nighttime (10:30 AM) and Aqua nighttime (10:30 PM), respectively.

10. A a Figure 4a: Monthly mean skin temperature from January, April, July, and October 2008 together with July 2007 for Beijing. Land cover type (defined in Table 1) is also presented along the longitude 116°E-118°E. Data is from Terra MODIS.

11. a. b. Figure 5: Box-plot based on April 2000 to December 2008 skin temperature observations over the 0.6°x0.6° selected box of Beijing and surrounding land cover regions and (b) New York City (NYC). Total 105 monthly values are examined. The top of the box represents the 75th percentile, the bottom of the box represents the 25th percentile, and the line in the middle represents the 50th percentile (i.e., median). The whiskers (the lines that extend out the top and bottom of the box) represent the highest and lowest values that are not outliers or extreme values (Wilks 1995).

12. 2. Urban Aerosol Effects • Jin, M., J. M. Shepherd, and W. Zheng, 2010: Urban Surface Temperature Reduction via the Urban Aerosol Direct Effect ------A Remote Sensing and WRF Model Sensitivity Study. Advances in MeteorologyVolume 2010 (2010), Article ID 681587, 14 pagesdoi:10.1155/2010/681587 • Jin, M. and J. M. Shepherd, 2008: Aerosol Relationships to Warm Season Clouds and Rainfall at Monthly Scales Over East China: Urban-land vs. Ocean • JGR, vol 113, D24S90, doi:10:1029/2008JD010276.

13. 0oC Cloud drop Rain drop Ice crystal Ice precipitation Aerosol Direct Effect: Scattering Indirect Effect: serve as CCN surface Aerosol reduce surface insolation

14. July 2005 Satellite observations Fig. 1, Jin and Shepherd 2008 Aerosol Distributions over Land and Ocean have evident differences

15. 3.3 Result: Diurnal Cycle of Urban Aerosols (Jin et al, 2005, JGR)

16. Figure 2. Interannual variations of urban aerosols over land (25N–35N, 110E–120E) and the sea off China (25N–35N, 120E–130E).

17. Figure 4. Scatter-plot between aerosol optical thickness and ice cloud effective radius. The data are sampled for July 2000, over the China Sea.

18. 3.3 (Jin and Shepherd 2008, JGR)

19. Figure 5. Scatterplot between aerosol optical thickness and water cloud effective radius. The data are sampled for Julys 2000–2004, east China urban regions (20N–40N, 115E–120E).

21. Figure 8. (a) Scatterplot of aerosol optical thickness and rainfall efficiency for rainfall events less than 0.5 mm/d, over the China Sea. The data are sampled for July (2000–2004). The red line is a linear regression based on original 5 July observations (blue dots); and the green line is the linear regression based on median. Median is calculated for each 10 optical thickness data. (b) Histogram of number of pixels as function of aerosol optical thickness.

23. Conclusion • Results from this study suggest that urban aerosols may have stronger effects on clouds than on rainfall. We found a detectable negative aerosol-cloud droplet size relation, especially over the ocean. • Aerosols may have different effects over ocean and over land. Over ocean, aerosols show significant effects on effective radius of liquid water clouds. There is less evidence for effects on ice clouds. On the other hand, over land (namely, continental areas with a large fraction of urban surfaces), no significant aerosol effects can be detectable in either water clouds or ice clouds.

24. Uncertainty Analysis • Using various satellite platforms to conduct research will, as always, raise concerns about the correspondence among the measurements.

25. 3.3 Aerosol effect on UHI

26. Aerosol reduction on Surface Insolation Using Chou and Suarez’s radiative transfer model

27. 3.4 WRF-urban model to examine relative contributions of different physical processes Aerosol Experiment 48-hours sensitivity study July 26-27-28 10-day sensitivity study Albedo Experiment Emissivity Experiment Soil moistre experiment

28. Aerosol Experiment for July 2008 WRF: Version 3 Domains: D1=18km; D2=6km Case: 00Z July 26, 2008; 48-h integration Domain Centre: 40.0N, 116.0E Beijing City: 39”56’N, 116”20’ Aerosol Domain: 39.7 - 40.1 N; 116.1 - 116.7 E SW reduced by 100 Wm-2 April 16, 2009

29. Domain 2: 6km Grid spacing Domains: D1=18km; D2=6km D1 D2 Beijing City

30. Green Vegetation Fraction: Beijing City Domain 2 Soil moisture at the first soil layer (10cm) Finer Domain

31. Case: 00Z July 26, 2008; 48-h integration Plots: from 00Z July 27 to 00Z July 28

32. Cloud Water (Qc) and Water Vapor (Qv) at 850 hPa & 700 hPa 850 hPa 700 hPa

33. Tsfc / T2m Diurnal change: Surface insolation reduced by 100 Wm-2 Tsfc T2m Tsfc decreases about 2-3 degrees

34. 00 UTC Control Run Sensitivity

35. 06 UTC Control Run Sensitivity

36. 12 UTC Control Run Sensitivity

37. 18 UTC Control Run Sensitivity

38. Surface flux / PBL change: Surface insolation reduced by 100 Wm-2

39. Winds at 950 hPa and 850 hPa Control Run Sensitivity 950 hPa Beijing City 850 hPa

40. WRF-urban simulated urban aerosol effects 10-day simulation

41. 3.4 Albedo Experiment for July 2008 WRF: Version 3 Domains: D1=18km; D2=6km Case: (1) 00Z July 25, 2008; 48-h integration (2) 00Z July 26, 2008; 48-h integration Domain Centre: 40.0N, 116.0E Beijing City: 39”56’N, 116”20’ Urban Domain: 39.7 - 40.1 N; 116.1 - 116.7 E Albedo: change from 0.15 to 0.10 April 26, 2009

42. Albedo Distribution: Albedo in Beijing city decreases from 0.15 to 0.10 06 Z, 2008-07-26 Difference of Tsfc because Albedo change

43. Tsfc increases about 1 degree at mid-day

44. 4. Future Directions • Simulate SF Urban System in WRF-CLM4-urban • Study urban impacts on local agriculture, for example, wine • Use WRF model to assess the relative importance of snow cover change overthe Sierra Nevada and urbanization to the regional water resources.

45. Summary • Urbanization has significant impacts on natural climate system, and thus shall be accurately simulated to predict such impacts. • Satellite remote sensing and regional climate model are extremely useful for understanding regional climate change.

46. Thank you.