1. Impact of Model Grid Size on Estimating Source Strength from Sand Storm Wen-Dian Lin, Tsun-Hsien Liu and Julius S. Chang National Central University Jhongli, Taiwan

2. Research Objectives Study on Impact of Asian Sand Storm Influence on Taiwan Air Quality and Control Strategy Use of Air Quality Model -- first question Impact of Model Grid Size on Estimating Source Strength from Sand Storm

3. Study Protocol MM5 Mesoscale Met. Model (81km) TAQM estimation of dust source and transport MM5 Mesoscale Met. Model (27km) TAQM estimation of dust source and transport Analysis of Differences

4. Modeling Domain Observation net resolution > 81 km D1:81km 73x97 D2:27km 82x121 D1 D2

5. Paramerization for sand dust source function Wang et al., 2000 JGR Surface friction velocity: u * >u * cri 25~70cm/s Relative humidity: RH<RH cri =40%-55% Cold front passage: T 24 -T 0 <-3 0 C Source function C: weighting factor for different land types u*:friction velocity RH: relative humidity R: fraction of the 12 bin of deflating yellow sand bin size from 0.13 to 20.13 μ m

6. RH cri

7. u * cri

8. Emission factor

9. April 8-11, 2001 Event

10. Event Meteorological Condition

11. TOMS AI Data 2001, April 8-11

13. TAQM Modeling ResultsResults

17. Unit: g/sec/km2 Average Emission Rates

18. Differences in Sand Dust Budgets and Distributions

19. TIME H

20. H

21. H

25. Time & Location 81km (ton) (A) 27km (ton) (B) Ratios (B/A) 2001/4/8/1 400UTC 105-109E 38-40N Total <4000m >4000m 68.861.6289.6% 68.861.5989.5% 000 2001/4/9/0 300UTC 112-114E 38-42N Total <4000m >4000m 4.066.66164% 4.06.4160% 0.150.26173% 2001/4/9/1 600UTC 114-118E 38-42N Total <4000m >4000m 8.6712.38143% 8.311.5139% 0.340.92271%

26. Conclusions For the same domain, difference in grid resolution has only small impact on average sand dust emissions rate. While the total budgets are similar there are differences in timing and spatial distributions. Initially, for the event studied, vertical distributions of mass budget in the source region can be different at around 10%. At near continental outflow region vertical distributions can be very different. For the event studied, at above 4 km such differences can be nearly a factor of 3.