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by: Adrienne Oberbrunner
Adrienne Oberbrunner

GPA 3.62

Irina Sokolik

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About this Document

Irina Sokolik
Class Notes
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This 0 page Class Notes was uploaded by Adrienne Oberbrunner on Monday November 2, 2015. The Class Notes belongs to EAS 8802 at Georgia Institute of Technology - Main Campus taught by Irina Sokolik in Fall. Since its upload, it has received 18 views. For similar materials see /class/233959/eas-8802-georgia-institute-of-technology-main-campus in Earth And Space Sciences at Georgia Institute of Technology - Main Campus.

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Date Created: 11/02/15
Effect of Air Pollution on Precipitation along the Front of the Rocky Mountains I m t w wwwwundergroundcom Uvervrew Inca Alston EA8 8802 Aerosols and Precipitation Outline Introduction Data amp Methodology Results Broad Conclusions Introduction Previous studies Givati and Rosenfeld 2004 found reductions in orographic precipitation of 1525 in California and Israel Previous studies Rosenfeld 2000 provide evidence of precipitation suppression due to urban pollution in shallow clouds Hypothesis increased pOIIULIUII UVUI lllULlUpUllLall area along the Front Range would lead to suppression of precipitation advected up the terrain orographic precipitation Specifically a noted decrease in orographic precipitation downwind ie west of Denver amp Colorado Springs eever amp Cotton 2007 Data amp Methodology Location Front Range ofthe Rocky Mountains extends meridionaIIy across the central the portion of northern Colorado with numerous cities along the eastern slopes Leeward side downwind side of the mountain range removed from moisture sources Pacific Ocean and Gulf of Mexi o Semi arid climate with rainy season April Sept Focused upon easterly Winds cammg IOWleVel moisture and pollution up the terrain van den Heever amp Cnttnn 2mm van den Heever a n d V r i aAg39gVJ 7 Dwig 39 Data amp Metodoloyh if 151 V39 Daily precipitation and wind data from seven stations from the NCDC for 1950 2002 Two groups of stations polluted and pristine relative to polluted sites with highly correlation precipitation Within each group compare sites directly downwind iewest and slightly elevated above urban sites along the Front Range Polluted sites Denver Cherry Creek Dam and Morrison Colorado Springs Colorado Municipal Airport and Ruxton Park Pristine sites Greely Data amp Methodology Wind data provided at 1 site Stapleton International Airport in Denver CO Lata IS wmd direction at peak wind gust Upslope winds peak winds from the NNE to SSE 20 160 Upslope winds gt upslope precipitation Upslope precipitation summed over entire year eever amp Cotton 2007 OEF orographic enhancement factor OEF Precip elevated sites precip lower sites Results TABLE 1 Summary of the trend analysis for the polluted and pristine sites along the Front Range Significance levels 5 b0 1 face type Station Location P value Endingstarting ratio Total precipitation Cherry Creek Polluted 026 119 Morrison PolluteL elevated 088 102 Morris nCllerry Creek Polluted 0 10 083 I eeley ristine 0 01 132 Waterdale Pristine elevated 033 113 GreeleyWaterdale Pristine 0 089 Upslope precipitation Cherry Creek Polluted 0 01 102 Morrison Polluted elevated 023 078 MorrisonCherry Creek Polluted 003 073 Colurado Springs Polluted 020 134 uxlon ark Polluted elevated 056 113 Ruxton Pai leolorado Springs Polluted 003 063 Greeley quot 39 013 136 VV Aterdale Pristine elevated 090 100 GreeleyWaterdale Pristine 013 070 I ee ey Pristine 013 136 Estes Park Pristine elevated 032 123 Estes ParkGreeley Pristine 0 31 084 van den Heever amp Cotton 2007 annual upslope precipitation mm annual upslope precip at Morrison mm Ending Starting ratio 144141 1 02 y 147 6x Ending Starting ratio 137176 0 1619 0 74 78 x r017 P 023 091 3 a Cherry Creek 1 Cherry Creek upslope 25 E350 142 mm annually 34 300 of yearly average 200 250 I o 39 E Morrison 156 mm 150 gFRv a 200 o o 5 annually 36A of yearly 00 quot 39 E 50 average o o o 1 mo 50 E 50 w Site trends are not 39 0 significant 1950 1950 1970 1980 1990 2000 1950 1960 1970 1980 1990 2000 Year M Strong statisical eVIdence Ending Starting ratio 0 971 347 egg Aw y369084x r071 F157 7 Logo p oo3 that lJpS39ope preC39p I 4 c 2395 d MorrisonChererreek Morrison decreased relative 350 12 o m 3g 27 tcc upilope precip Cherry E ree 250 39 The OEF l by almost 30 20 EL i in upslope OEF is larger 395quot and more significant than 100 fortotal precip 3 airflow so g over urban areas is a i i o i 1 i i affecting the precipitation 0 50 1 re Q50 ma a 3 0 1950 1960 1970 V 1900 1990 2000 process at the elevated Fm 4 Same as Fig 2 but considering only upslope pi39ecipilalion sites annual upslopa Fleclpllatlon mm 1550 Ending starring ratio 135100 1 36 1360 19m lean two 2000 Vaar 50 on an 200 250 annual upnop preclp alGreeley mm FIG 7 Same as ralia of annual upslope precipitatinn 1950 1950 19m 1950 raar 990 2mm Greely amp Waterdale receive more than a third of yearly precip from upslope events Neither has a significant trend in precip There is no significant trend in the OEF additional support that precipitation suppression occurs west of Denver amp Colorado 8 rins ie polluted areas because of air pollution Conclusions No statistically significant trends found in the OEF for total precipitation Si39nificant trends found in OEF for u slo e recipitation for Denver amp Colorado Springs sites 2 30 decrease yet no trends found for pristine sites gt hypothesis true Results consistent with Givati amp Rosenfeld 2004 study that yielded a 1525 reduction in orographic precipitation General conclusion Urban pollution can decrease 7 recr Itatlon In shallow clouds eever amp Cotton 2007 10 awnwnd COMactive Storm Outline Introduction Model and experiment setup High background aerosol concentration results Low background aerosol concentration results Conclusions Broad Conclusions wm Wth a WW eever amp Cotton 2007 12 Introduction MET WW JVed wuts of enhanced summer precipitation over St Louis MS by 525 over background values 5075 km downwind of the city T thunderstorms associated with T population in cities Urban areas enhance lightning activity Why Many hypothesis Cotton 2007 Introduction 1 Greater aerosol concentrations within urban regions act as CCN giant CCN GCCN and ice nuclei IN 2 Increased surface roughness of urban areas leads to enhanced surface convergence over and downwmd of the urban region 3 The urban canopy diverts thunderstorms around urban regions 4 The urban regions serves as an enhanced source of m0Isture 5 Sensible and latent heat fluxes within the urban region and thermal pertubations of the boundary layer by the urban heat island UHI affect moist and dry convection van den Heever amp Cotton 2007 14 Introduction GCCN CCN s with a radius gt 1 pm Surface roughness manmade surfaces have more roughness than natural materials Urban heat islands artificial surfaces have different thermal properties such that they are more capable of storing solar energy and converting it to sensible heat causing air in urban areas to be 2 10 warmer than surrounding nonurban areas most notable on a clear windless night eever amp Cotton 2007 Introduction Hypothesis to investigate e pacts c urbanenhanced aerosol concentrations on convective mm development and predication over and downwind of St Louis MO ultimately to make a conclusion about which factor is dominant in convecmc 0 dcwwp t a u precipitation Model and Experiment Setup 39m Case study J EnvironmentiA On June 8 19 flow in additior a a 1700 UTC by 1500 UTC arm and moist 3an tropospheric ated and transient nature of the s or 1900 UTC entative of conditions duri A Storm activity early evening I considerable Vl Huff and Voge storms in the a Same case stL M amuou39r 1 ted through the all and EX 43 0f the van den Heever amp Cotton 2007 st southwest 02200UTC 39 so wt d y 9 We a H 1 a a FIG l Composite rmlm images mer St Louis for a 17001b 1500 El l900dl1UOD e 17 2mm and m 7700 UTC 2 Jun my mm Rozorr er 1 r7001ne image was Adapted Mm perumsmn of c Ruzolr Contour Human me pmva every 10 an Model and Experiment Setup Model aspect Grid Initialization Time ste Simulation duration Microphysics scheme Convective initiation Boundary conditions Turbulence scheme Radiation scheme Surface scheme van den Heever amp Cotton 2007 1039w 95w l hail all activated 200 400 600 800 10001200 FIG 2 The location of grids 173 for the simulations described in the text The field shown is topography In idi cations by Lilly 1962 and b39 v v LEAF2 Walko et all 2000 coupled with the TEB model Masson 2000 for urban regions Model and Experiment Setup 1500 UTC 1900 UTC I 39 1 gun 3 m x n I 39xx a r N lU 39M R if 2000 355quot 2000 FIG 3 The locmiou of IL downwind calculmions Icfcrlcd L0 in 119 text is shown Ivy lhc rectangular box Ch Lunceulmlion buline 1300 and 1500 cmquot al 270 m AGL 11 indiculud b he Llullrd 1hchle SL Louis igt 51mm m a Surf 2 mm m 15 n m AJ3L are mdk aled by me nun and me 39 015 200 UTC i huwu in he n punt b the 3 I link Hum van den HeeverampCununZDD7 19 Results H 1700 UTC UHI develops for all simulations were the city is included UHI intensified around 1600 UTC and by 1800 UTC a heat island of 2 C had 1900 UTC formed Water mixing ratios over the city are lower than in surrounding rural area Wind convergence over and downwind of urban area 05 0 05 1 15 2 25 no4 39 39 quotNullxrn P s k lowesz model level 43 m Tempemuue T is shaded water vapor mixing ratio g kgquot is indicated using thick black conlonxs a l g kgquot imervals and rivers and St Louis are indicated using min white Lines Wind vectors for me RURALVH are also indlcnled lae scale of which is indicated al me nonom oi me gure 2000 UTC 2015 UTC 2030 UTC bdbatimecxbrb39 npmicaftrs 39quot daydknp wnm39rrdila r to MN th itoltbaseamm39 to the 39 MSWdime city Stamnmxetioml stsf 2045 UTC 2115 UTC my themyzubuareps 15 m 1 1 mian e e 6gggighnan in RU V4 51ml ar to observed 0 5 a a Emmdmhr mghts R thei39mutatetdtsibrms lag 2130 UTC 2145 070 22100 010 VMiomwedmms cobrpa39thmtksn can 39 l A have on the dynamics 039 of the storm 330511 3 A L 91W 905w 90W 91W 905w 90W 91W 905w 90W lt 1200 1500 1300 F15 7 Same as m Fig 5 but m the URBANM semiuuty test run ctm ny 21 11h mu 1111mmNJanmnuruu1mm wmnguucx 1mm hum lm xnv 391ml1nv n 0101110111000 5 101m iummuud 1 1mm hm hm 2000 UTC 2015 UTC 2030 UTC 39quotquot x o KJN m 355N 0 r a I a 139 2045 UTC 2100 UTC 2115 UTC 39w x 7 L N t taL a I 39 39 I 1 quot 385N 9 9 a 7 a r a z 0 1 2130 UTC 2145 UTC 2200 UTC x 39N 0 o r x 39 39t J 4139 385N 7 o 0 siw 905w sow 91W 905w 90W 1200 1500 1800 91W 905w 90W FIG ll Same a m Fug 5 hut tor the URBANL smmlmmn Greater dim aesqt tprm MAQIIJH dioesn t URBAN L when cmp 6e91to High amlamem NW of CiStorm to the net mt m atrs teruEW 9y the aNQW EtQFWeCiP EWQWMWE of wqmwrnch in Macare affected 1 by urban aerosol concentrations Results a Cloud b Rain 2200 200 250 200 Pristine 150 150 A 100 100 50 50 o I I 0 I I 0 I I 2000 2100 2200 2000 2100 2200 2000 2100 200 ds w 200 200 Graupel 2200 0 0 I o I 2000 2100 2200 2000 2l00 2200 2000 2100 200 gHail 200 hLiquld ZOO Dice 150 lOO so 7 n I 0 I I n I I 2000 2100 2200 2000 2100 2200 2000 Zl 00 Time UTC Time UTC FIG 14 Same as in Fig 8 but for the lower background aerosol Concentration tests Time UTC 2200 39 Q39E I I FIWSHQHE n m f 39f d d l f and G93ng EEI S ERPRHW 035209 08 9 20833 489000 reil g gss V0050 in for B Q riQo 39wg ll FSI Atte fMBAlhet dbend reveris eas w mnb LWIOIWWWIH mQUSrE P Mt t i tc Bil eme atwenm raiwmsdsmedlwrtth Gmmmmmm 21000020345 UTC Major differences between Fig 8 and 14 1 T hydrometeor mass for lower concentrations 2 trends in each simulation similar Fm is Same ns in Fig 0 but or he lmverrbackgroundracl39osoltoncenlra on lists F6 9 Time series of the accumulated olumsuic precipilar lion in he downwind region expressed as a percentage of the URALVH simulation Similar trends for both cases where GCN and URBAN initially produce more precipitation yet trend reverses after 2115 UTC Low concentration simulations yield increased downwind precipitation V3 E EVE Efll f i ence between runs high as 30 2 a Maximum Updra s iiis 0 39 39 2000 2100 2200 000 2100 2200 Time UTC Time UTC FIG 13 Time series oi the maximum downdrati Within the downwind region for he sensitivin lesis described in he Iexr Stronger updras between 000 and 2100 U C L and URBANL with reversal to CCNL and RURALL becoming dominate afterwards which coincides with the time of storm splitting New updrafts develop downwind earlier in the RURALL and CCNL around 2145 UTC The downdrafts show a similar patter to the updrafts where vandemeevereghgguded GCCNL and URBANL develop downdrafts later after 25 210 U C Conclusions While urban enhanced aerosols have numerous effects on the microphysics and dynamics Of the dOWnVVII Iu LIUI Ivcbuvc aLUIIIIa II I u IU convergence effects driven by the urban land use characteristics that determine whether convection will actually develop shown by sensitivity test without the city Enhancements of GCCNs yield increases in cloud water rain updrafts and downdrafts initially than control run Enhancements of CCNs delayed the formation of cloud water rain updrafts and downdrafts however as time progressed enhanced CCNs and control run produce more cloud water rain and earlier updrafts and downdrafts Appears that the delay in the updraft and downdraft development in the CCNL case and the influence of this on storm dynamics and subsequent storm development tend to offset the adverse effects of suppressed warm rain processes Because the lower concentration simulations 1 ielded such significant increases with respect to high concentrations this implies that areas that are less industrialized or near coastlines will notice a greater effect of downwind urban aerosols van den Heever amp Cotton 2007


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