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Bereket Lebassi Habtezion Ph.D. Candidate Prof. Jorge Gonzalez Advisor

Bereket Lebassi Habtezion Ph.D. Candidate Prof. Jorge Gonzalez Advisor Department of Mechanical Engineering Santa Clara University Presented at CCNY 04 May 2010. Observational and Modeling Study of Urbanization vs. Global Warming Impacts on SoCAB and SFBA Climate. Outline.

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Bereket Lebassi Habtezion Ph.D. Candidate Prof. Jorge Gonzalez Advisor

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  1. Bereket Lebassi Habtezion Ph.D. Candidate Prof. Jorge Gonzalez Advisor Department of Mechanical Engineering Santa Clara University Presented at CCNY 04 May 2010 Observational and Modeling Study of Urbanization vs. Global Warming Impacts on SoCAB and SFBA Climate

  2. Outline • Background and Hypothesis • Observational Study • SFBA and SoCAB analysis • Impacts on Energy • Simulation Setup • Grid Configuration • Land Use input • Anthropogenic heating • Results & Validation • GHG impacts • Urbanization impacts • Conclusion

  3. Motivation 1: Global Warming • Earth has warmed approximately 0.2 K/decade for past 30 years, with max • warming after 1970. • Land temps has warmed faster than SSTs From NASA RESEARCH NEWS (2006), group led by James Hansen, GISS, NYC

  4. Motivation 2: Interaction of coastal climate influences • Global • Sea surface temps (SSTs) • ocean currents • GC pressure systems • Mesoscale • sea/land breezes • mt/valley breezes • ocean upwelling • Land-use &/or Land-cover (LULC) changes • Urban heat islands (UHIs)

  5. Earlier studies have related climate-change to increased (*=CA studies; modeling studies in yellow): • SSTs, evap rate: *Goodridge ‘91, Karl et al. ‘93 • Cloud cover changes: *Nemani et al. ’01 • Upwelling: *Bakun ‘90,*Snyder et al. ‘03; McGregor et al. ‘07 • Anthropogenic land cover conversions:Pielke et al. ’07, Chase et al. ‘00; Mintz ‘84; Zhang ‘97 • Irrigation: *Christy et al. ’06, Lobell et al. ’06, *Kueppers et al. ’07, *Bonfils et al. ’07 • GHGs: *Duffy et al. ’06, Walters et al. ’07, Cayan et al. ‘08 • UHIs: Ladochy et al. ’07

  6. The (LCLU + GW) Question on Urban Coastal Areas • What is the relative climatic impacts of global climate change in urban coastal regions? • Under these conditions of LCLU and global climate change, what are the combined effects in sea breezes, surface temperatures, precipitation, and extreme events?

  7. Current Hypothesis: Observed Calif temp trends resulted from • GHG WARMING/LULC • and/or • b. INCREASED INLAND WARMING • INCREASED HORIZONTAL T- & p-GRADIENTS • (COAST TO INLAND) • INCREASED SEA BREEZE: FREQ, INTENSITY, • PENETRATION, &/OR DURATION  • COASTAL REGIONS DOMINATED BY SEA BREEZE SHOULD THUS COOL DURING SUMMER DAYTIME PERIODS

  8. DATA • NCDC DAILY MAX & MIN 2-METER TEMPS FROM 273 CALIF SITES (SEE MAP below) FROM 1948-2005 • NCDC MEAN MONTHLY GRIDDED SSTs • INTERNATIONAL COMPREHENSIVE 0CEAN-ATM DATA SET (ICOADS): 1880-2004 • 2 OR 1 DEG HORIZ RESOLUTION • SCU DOWNSCALED REGIONAL CLIMATE CHANGE MODELING RESULTS FOR CALIF (10 KM RESOLUTION) FOR 21ST CENTURY (SEE MAP below)

  9. ANALYSES • Only data from 1970-2005 (due to accelerated warming in the period) were used • Annual & summer (JJA) warming/cooling trends calculated (0C/decade) for SST, Tmax, Tmin • Spatial distributions of JJA Tmax trends plotted for • South Coast Air Basin (SoCAB) • SFBA and Central Valley (CV) • JJA land-sea T-gradient (as surrogate for p-gradient) trends calculated from • mean monthly SSTs • 2-m land Tmax values

  10. SCU (Maurer) statistically 10-km downscaled 1950-2000 mod-eled JJA temps (0C) show total warming rates that decrease to coast (Dots are Calif NCDC sites & boxes are study sub-areas)

  11. Result 1: Lebassi et al. (2009) J. of Climate Observed 1970-2005 CA JJA max-Temp (0C/decade)trends in SFBA & SoCAB showed concurrent: > low-elev coastal-cooling & > high elev & inland-warming > signif levels: solid circles >99% & open circles <90%)

  12. Results 2: Same for SFBA & Central ValleyCOOLING AREAS: MARIN LOWLANDS, MONTEREY, SANTA CLARA V., LIVERMORE V., WESTERN HALF OF SACRAMENTO V.

  13. Results 3: Temp. trends for all of California Tmin (Curve b) increasing faster than Tmax (Curve c)

  14. Result 4: Combined SFBA & SoCAB 1970-2005 summer trends (oC decade-1) of Tmax (Curves c) Inland Tmaxwarming sites Coastal Tmaxcooling sites (a) (b) (c) (d)

  15. Result 5: Average JJA 1.4 deg ERA40-reanalysis SLP trends (hPa/decade) at 11 LT for 1970-2005 - • Arrow shows SLP-gradient calc. end-points • Plus & minus are High & Low pressure centers, respectively. • p-increases (up to 0.34 hPa decade-1) in Pacific High • p-decreases (up to -0.8 hPa decade-1) in Calif- Nevada thermal Low • p-gradient trend in next slide + +

  16. Result 6: Trend in ocean-land summer SLP-gradient (hPa 100-km-1 decade-1) at 11 LT at end-points in previous slide Results show: p-gradient increases in both areas  increased sea breeze

  17. Result 7: Implications on Calif Energy UsageLebassi et. al (2010) J. of Solar Energy and Sustainability (a) Cooling Degree Day (CDD) trend: upward due to GHG warming  More energy for cooling (b) Heating Degree Day (HDD) trend: downward due you to GHG warming  Less energy for heating

  18. Result 8: Peak Summer Electricity Trends for 1993-2004 in (Kw/person/decade) from LA Dept of Water & Power (LDWP), Pasadena, & Riversides • Results show: • Coastal LDWP & Pasadena: down- ward trend • Inland Riverside: upward trend

  19. SUMMARY 1: OF OBS STUDY • SUMMER DAYTIME MAX-TEMPS HAVE • COOLED IN LOW-ELEVATION COASTAL AREAS • WARMED IN INLAND AREAS • PREVIOUS STUDIES DREW WRONG CONCLUSIONS B/C • They did not separate summer vs. winter, day vs. night, &/or inland vs. coastal • Therefore, their Tmax were wrong and thus their Tave & DTRs were contaminated

  20. Modeling Effort Introduction to Regional Atmospheric Modeling System (RAMS)

  21. RAMS RANS Cartesian Equations Km, h: eddy diffusivity coef. for momentum & heat. Momentum eqs for u, v & w (1) (2) (3) Latent heat & RFD Local ∆ = Advection + p-grad + Coriolis + Turbulent Diffusion Thermodynamic eq for ice-liquid water potential-temp Water Species (n-species, e.g. vapor, ice, snow, …) Sources & sinks via phase changes

  22. Continuity eq for π (4) (5) (6) (7) Exner function for pressure Ideal Gas Law for density Poisson eq for Tv • In summary: • prog eqs for u, v, w, өil, rn, π′ • diag eqs for π, ρ, p, Tv

  23. Vertical Diffusion Coef Km,h,e via TKE (e) Shear Production Buoyancy Molec Dissipation Sm,h,e are f(Ri) l is mixing length

  24. Vertical Boundary Conditions • z= H (model top) = 18.8 km • Rigid lid, with Rayleigh friction layer of 4 km • w = 0 • z= h (SBL top) = 50 m • Continuity of fluxes, gradients, & profiles • z= 0 (sfc) • Sfc energy balance Eq in LEAF3 • No slip BC: V = 0 • z=Hs (bottom soil layer) =1 m • Constant temperature from large scale model

  25. For sfc BC for T(t): RAMS uses LEAF-3 “big leaf” model to solve sfc energy balance at each sfc-type, e.g., for all-urban (no veg or evaporation) sfc • Terms on RHS of eq (L to R): • ↓ solar rad absorbed at sfc • ↓IR rad from atm absorbed at sfc • ↑IR rad from sfc • ↑IR rad from urban sfc • Note: rad terms come from complex rad transfer model • convective heat to atm [where ( )* quantities come from SBL-eq ] • ground heat to atm (where өs comes prog soil temp eq) • anthro heat to atm. (specified, in up-comimg slide) • Finally: sum of RHS terms yields trend of building canopy temp θu, which When added to past value gives current value.

  26. Parameter values for different urban classes where all symbols are defined as: α Albedo ε Emissivity FV Vegetation Fraction HV Vegetation Height

  27. RAMS simulations of SoCAB Area

  28. Selected past (1965-70) & present (2000-2005) simulation periods have similar PDO & temp variations  large scale variability effects are eliminated Note: ENSO impacts are mainly in winter in this area

  29. Methodology • Research goal: separate-out effects of urbanization & GHG warming on • observed Lebassi et al. (2009) SoCAB JJA max-temp trends • use RAMS to simulate these changes • RAMS simulations • Runs 1 vs. 3: • Research question: Effects of global climate-change? • Run 1: current • urban LULC (NOAA 2002) at 30-m resolution • global-climate & SSTs for five JJA-periods (2001 to 2005) • Run 3: uses • Run 1 (Current 2002) LULC • global climate & SSTs for five past JJA-periods (1966 to 1970) • Runs 1 vs. 2: • Research question: Effects of urbanization? • Run 1: one-year of Run 1 (2002) • Run 2: pre-urban • LULC: all urban turned to local dominant class, i.e., scrubland • over-estimate of max urbanization effects • 2002 JJA global-climate & SSTs

  30. ICs and Large-scale BCs (FDDA) • Model initialized • 0000 UTC = 17 LT • 1 June of given year • 12-hr spin up: 1st night • Large scale BCs • every 6-hr • from gridded NCEP global-model output

  31. Grid Configuration • > Arakawa-C staggered grid • Horiz nested-grid resolution • Grid 1: 20 km • Grid 2: 4 km • Vertical Grid >49 levels to 31 km • Δz = 40 m (near sfc) • 1.15 stretch-ratio • Δz =1.2 km (aloft)

  32. + + + + • Grid 2 (4 km): present (2002) LULC-classes • Lines: key topographic-heights (+ = peaks) • Input: 30-m NOAA LULC  RAMS’s Leaf-3 classifications • Output colors: dominant class; parameter values as weighed averages • Veg: greens • Urban: browns • Black squares: METAR stations for RAMS evaluation

  33. New Tech: determination of urban Veg, Rooftop, & Street fractions (a) (b) Resulting 1- color visible image: 32% is veg & 68% is roof + street Initial visible Google map for typical urban class 19 (c) • Methodology: • Start w/ visible Google map for typical SoCAB urban area (Map-a) • Change Map-a to 16-color image (Map-b) & count fraction of green pixels (32%) • Change Map-a to 2-color image (Map-c) • > where white fraction is rooftop & • black fraction is thus veg + streets • > Street fraction is thus black fraction • minus green fraction (from Map-b) • Only veg fraction info can be input into current RAMS lookup-table > Resulting 2-color visible image: building are white (52%): & vegetation + streets are black (48%) > Thus (48-32%=) 16% are streets

  34. Anthropogenic heat flux: Sailor and Lu (2004) Where: • ρpop(t) Population density [person/km2] : from US census • FV(t) Non-dimensional vehicle traffic-profile (lower right slide) • EVVehicle energy-used [W/km]: from DOT • DVD Distance traveled per person [km]: from DOT Traffic-profile (%): red is US & blue is LA Summer CA-building electricity fraction Total profile

  35. Model Validation with Run-1 (current met & LU) output: June 1-10, 2002; averages for 12 SoCAB METAR sites Where: blue is obs & red is closest RAMS grid point Mean wind speeds: both at 10-m Mean temps: both at 2-m Model =3.1 m/s vs. obs = 2.9 m/s Model = 20.2oC vs. obs = 19.3oC

  36. (a) Model vs. Observation Correlation red wind, blue temp, (b) JJA daily Tmax averaged over 15 COOP station (c) Model vs. Observation Correlation for (b). • Correlation: • Temp: r2 = 0. 87 (blue) • WS: r2 = 0.82 (red) • Past Validation: • 1970 JJA Tmax • Model (red); Obs (blue) • Tmax ave diff = 0.7 oC • Correlation: • Tmax: r2 = 0. 70

  37. RAMS Results 1:19-m spatial-patterns Temp and wind results from • Run 1: current climate and current urbanization • Run 2: current climate and no-urbanization • Run 1 minus Run 2 • Run 3: past climate and current urbanization • Run 1 minus Run 3

  38. GHG WARMING RESULTS:NEXT 10 SLIDES

  39. Now Past • ICOADS BC-SST input to RAMS • Box is D-2 • RAMS-interpolated D-1: JJA 5-yr ave. • (constant for given summer) • Top L: Run-1 SST (orig. resolution: 1 deg) • Top R: Run-3 SST (orig. resolution: 2 deg) • Lower: Run-1 minus Run-3 SST (N-P) • Large-scale SST results: • NW-cooling is also a large-scale effect • warming has max-change in south N- P

  40. H H L L Now Past • NCEP SLP 17-LT JJA 5-yr Aves. • Top L: Run-1 (orig. resolution: 2.5 deg) • Top R: Run-3 (orig. resolution: 2.5 deg) • Lower: Run-1 minus Run-3 (N-P); Dashed • box is p- calculation in observational study • Results: • Location of H: didn’t change much • Mag diminished over most of ocean • Peak change over center of H • Increases both N & S of center H • Max decrease over Mx coast due to • expansion of L + - - + N- P

  41. H H C C Now Past T(K) Present & Past 17-LT JJA-ave NCEP 1000 hPa T(K) • BC input to RAMS every 6-hr for periods of Run-1& Run-3 • Results: Hot inland (H) & cool ocean (C) • Centers of hot & cool moved to SE; White boxes D-1 & D-2 • Changes best seen in next slide

  42. N - P N - P + + - - Present minus Past 17-LT JJA-Ave NCEP 1000 hPa ΔT(K) • Right slide: horizontal section • Boxes are D-1 & D-2 • Area of slide: only west part of prev SLP slide • Dash-line: z-section in slide at Right • Results: • Inland warming (+) & off-shore cooling (-) • Center of cooling is b/t coast & • center of H (previous slide) • Left Slide: vertical section (from Fig on right) • Violet-line is land-area • Green D-1; White D-2 • Results: • cooling up to 980-hPa or 400-m • Max warming at 350 hPa or 1.6 km

  43. 12 LT 14 LT • RAMS Run-1 (present) JJA-Ave D-1 T(K) & V (barb = 1 m/s); Box is D-2 • Results: • Cool: ocean & Mt-coastal areas • Warm inland • 12 LT: SB & upslope flows started • 14 LT: Both flows more-developed • 16 LT: combined SB & slope winds 16 LT

  44. 14 LT 12 LT • RAMS Run-1 (present) minus Run-3 (past) JJA-Ave D-1 T(K) & V (barb = 0.4 m/s); Box is D-2 • Results: • Ocean warming < inland warming • 12 LT: change in T & SB started; • coastal cooling started • 14 LT: SB accelerated; coastal • cooling filled the basin • 16 LT: SB started to slow down; • coastal cooling reached max 16 LT

  45. RAMS JJA-Averaged D-2, ∆T(K) & ∆V (barb = 0.5 m s-1) • Results: • Ocean warming < inland warming • 12 LT: change in T & SB started; coastal cooling started • 14 LT: SB accelerated; coastal • cooling filled the basin • 16 LT: SB started to slow down; coastal cooling reached max • Inland warming (up to 2.0 k) greater than SST warming (up to 0.5 K). • GHG warming over land (1-2 K)  increased sea breeze flow (1-2 m/s)  cooler temps over coastal areas (up to -1 K) • Stronger HPGF accelerates on shore directed flow (by 2 m/s), • Statistical Analysis is seen on the Next slide 12 LT 14 LT 16 LT

  46. Two tailed stat. sig. values for for the T, U & V T U V 19 UTC 21 UTC 23 UTC ∆T: The coastal cooling, the SST change, and the inland warming are significant at >99%; Less significant (at down to <90%, light yellow) results due to cancellation of larger GHG warming by cooling due to increased marine flows ∆U and ∆Vl: Most of the change in the u & v winds are also significant at 99%. There are less significant areas over the ocean (19 UTC) when the sea breeze change is not strong and over the land (23 UTC) when the sea breeze starts to weaken.

  47. Past Now • Vertical cross-section at 33.85N • Temperature & wind • Top right Run-1 (present): cold to 500 m; warming in the inland valleys & hills; inversion top at 900 m; inversion base at 50 m • Top left Run-3 (past): same as left; inversion top at 750 m; no inversion base detected, • Bottom right Run-1 (present): • Shallow warming over the ocean, due to the SST increases • Coastal cooling over land; inland warming over inland valleys and hills • Another cooling layer over the ocean (up to 500 m) due to large scale cooling N - P

  48. Stat. sig. for the vertical cross section of temperature changes of Domain-2 at 33.83 N • Bottom left, statistical sig. for the difference field: The SST warming, the cooling over the ocean and the coastal cooling are significant at > 99%.

  49. Vertical cross of w (cm/s) at 14 LT • Top L Run-1 (present):Subsidence over the ocean; upwared motion over land • Top R Run-3 (past): Similar to Run-1 • Bottom: Run-1 minus Run-3 (N-P) • Subsidence increased • Increased upward motion over the coastal plain and inland hills; separate from the ocean

  50. URBANIZATION RESULT: JJA 2002, 19, 21 & 23 UTC: Run 1 minus Run 2 Temp & Wind Differences 12 LT Urban: Urban area warming (up to 1.0 K); Sea breeze retardation i.e. Run-1 vector is onshore & difference vector is still offshore due to z0-deceleration) Rural: still some warm air adv, small warming (up to 0.2 K) ; mountain top has still cooled perhaps due to induced secondary-circulations 14 LT 16 LT T (K)

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