STATE OF THE CLIMATE IN 2009

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not inconsistent with expectations during a developingEl Niño episode (see sidebar).Fall 2009 was a season of extremes for the contiguousUnited States. While September was about0.8°C above the long-term average, October wasmarked by an active weather pattern that reinforcedunseasonably cool air behind a series of cold fronts,creating an average temperature that was 2.0°C belowthe long-term average and ranked the nation as thefourth coolest October on record. During this month,43 of the lower 48 states averaged temperatures thatwere below normal. Florida was the only state withan above-normal temperature for October. The followingmonth was something of a mirror image,becoming the third warmest November on record,2.2°C above the long-term average. Overall, thenationally-averaged temperature for the three-monthautumn period was above-normal, ranking as the34th warmest on record.The average annual temperature for Alaska in2009 was 0.5°C below the 1971–2000 long-term average.This represents the second consecutive annualperiod in which Alaska has experienced cooler-thannormaltemperatures. Seasonal anomalies contrastedthe contiguous United States, with both winter andspring temperatures below average. The summer andfall seasons were warmer-than-normal as 500 mbheight anomalies increased.Fig. 7.4. Statewide ranks of (a) 2009 temperatures and(b) 2009 precipitation. A rank of 115 represents thewarmest/wettest year since 1895. Much above-normaltemperature/precipitation is defined as occurring inthe top 10% of recorded years, which correspondsto a rank of 105–115. Above-normal temperature/precipitation is defined as occurring in the warmest/wettest third of recorded years (ranks 78–103). Muchbelow-normal temperature/precipitation is likewisethe bottom 10% of coolest/driest years since 1895, andbelow normal is defined as the remaining coolest/driestthird of the distribution. (Source: NOAA/NCDC.)(ii) Precipitation and snowpackAverage precipitation for the contiguous UnitedStates in 2009 was 64 mm above the long-term averageof 740 mm. Precipitation across the United States in2009 was characterized by persistent wetness in theMidwest and Southeast, while precipitation in theWest, Northwest, and Southwest was below average(Fig. 7.4b). Arkansas observed its wettest year onrecord with four months of top three precipitationranks (May, wettest; July, third wettest; September,second wettest; October, wettest). The unrelentingweather pattern also contributed to the second wettestannual period in Alabama and Illinois. Morethan half of the contiguous United States receivedabove-normal precipitation for the year. Conversely,the lack of monsoonal moisture in the Southwestcontributed to Arizona’s fifth driest annual period.The decadal trend of the contiguous United Statescontinued its above-normal precipitation streak withthe past decade (2000–09) averaging 18 mm abovethe 20th century average and precipitation over thepast four decades averaging 27 mm above the 20thcentury average.It was the 22nd driest winter (December 2008–February 2009) for the contiguous United States inthe 1895–2009 record. Texas recorded its driest winterperiod, while North Dakota experienced its wettestwinter on record. The contrasts in rankings were theresult of an active upper-level pattern that shuttledsystems rapidly across the northern-tier states, whilebypassing the deeper south. Conversely, the contiguousUnited States experienced its 18th wettest spring(March–May). Relatively slow-moving storm systemsand surface fronts across the southern United Statesled to above-normal precipitation averages acrossthe southeastern United States. Georgia experiencedS138 | juNE 2010
its second wettest such period. Several other statesexperienced a spring period that saw above-averageprecipitation: Florida and Illinois (fifth wettest each),Alabama (seventh), and Arkansas (ninth). In March,record flooding occurred in parts of Minnesota andNorth Dakota along the Red River. The flooding waspreconditioned by copious winter precipitation coupledwith persistent precipitation-producing stormsin the spring. Record-high flows were recorded alongthe Red River with peak levels exceeding the 500-yearreturn interval.Summer (June–August) precipitation was variablein 2009, which is typical for the season, but overallnear normal, ranking 54th wettest out of 115 years.Regionally, the Northeast had its second-wettestsummer on record, continuing a string of abnormallywet summer periods. Deficient monsoonal rains inthe Southwest contributed to Arizona’s third-driestsummer. Precipitation averages in Georgia and SouthCarolina were also much below normal. Conversely,Massachusetts experienced its wettest summer and itwas Maine’s third-wettest such period.It was the 11th wettest autumn (September–November)on record for the contiguous United States.Anomalously wet conditions in October led to arecord wet month for the nation as a whole. Thenationwide precipitation of 105.4 mm was nearlydouble the long-term average of 53.6 mm. Persistentprecipitation during September and October madeArkansas’ autumn precipitation its greatest ever.Nine other states were much above normal in termsof precipitation for the autumn season. Interestingly,these high precipitation anomalies occurred despiteonly two tropical cyclones (Tropical Storms Claudettein August and Ida in November) making landfallduring the Atlantic Hurricane season. The variableclimatic extremes continued in November when theupper-level jet retreated to the north, contributing toa nationally-averaged precipitation that ranked 18thdriest, continuing the run of below-normal Novemberprecipitation in the contiguous United States. Thesummer and fall months were drier than average inmuch of Alaska.During winter 2008/09, snowpack levels werebelow- to near-normal for the Cascade Mountainsand the Northern Rockies in Idaho, Montana, westernWyoming, and Utah. The Olympic Mountainsand Okanagan Highlands of Washington had snowlevels less than 50% of normal. The Sierra Nevadasalso experienced below-normal snowpack for theseason. Conversely, the central and southern Rockiesin Colorado, New Mexico, and northern Arizonahad above-normal snowpack totals by the end of theseason. Alaska snowpack was generally above normal,with the exception of the northern and southerncoastal regions of the state.March brought several large snowstorms thatbroke daily and monthly snow records across thecenter of the country. Statewide records for 24-hrsnowfall accumulations were observed in Texas (64cm), Oklahoma (66 cm), and Kansas (76 cm). Seasonalsnowfall records were measured in International Falls,Minnesota, with 318 cm and Spokane, Washington,with 248 cm of snowfall.The beginning of the 2009/10 snow season broughtbelow-normal snowpack to the western United States,including much of Alaska, while Arizona and NewMexico observed above-normal snowpack. The lowsnowfall amounts contributed to ongoing drought inCalifornia. October and December were particularlysnowy across the contiguous United States, with bothmonths setting new snowfall extent records. Octoberwas North Platte, Nebraska’s snowiest month onrecord with 77 cm, while December brought recordsnowfall to the Northeast corridor and the Plains,including Philadelphia, Pennsylvania; Washington,D.C.; and Oklahoma City, Oklahoma.(iii) Droughts and wildfiresWidespread precipitation extremes occurred during2009, with large areas (20–25%) of the countryvery dry (monthly precipitation total in the bottomtenth percentile of the historical record) during January,February, and November and large areas very wet(top tenth percentile) during May, June, October, andDecember. The dryness exacerbated areas of droughtduring early 2009 while the abundant precipitationbrought drought recovery during the later months.The year began with 19.2% of the contiguous UnitedStates experiencing moderate to exceptional drought,as defined by the U.S. Drought Monitor (USDM). Thatpercentage increased to 26.6% by late March beforedecreasing during the summer and fall, ending theyear at 12.4%, which was among the lowest valuesin the ten-year USDM record. Based on the 110-yearPalmer Drought Severity Index (PDSI) record, 2009capped a decade of expansive drought, with the2000–09 decade ranking as the third biggest droughtdecade in the last 110 years.The drought epicenters during 2009 were southernTexas, the southern Appalachians, California, andHawaii. Severe agricultural impacts were felt, especiallyin Texas and Hawaii. Low streams, reservoirsand stock ponds, and depleted soil moisture combinedSTATE OF THE CLIMATE IN 2009 juNE 2010 |S139
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Luo, Jing-Jia, Research Institute f
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Tedesco, Marco, Department Earth an
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4. THE TROPICS.....................
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ABSTRACT—M. O. Baringer, D. S. Ar
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I. INTRODUCTION—M. O. Baringer an
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Table 1.1 The GCOS Essential Climat
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S18 | juNE 2010
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Stratospheric TemperatureCloudiness
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Source Datasets Sectionhttp://www.p
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HOW do WE KNOW THE WORLD HAS WARMED
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Fig. 2.6. As for Fig. 2.1 but for l
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Fig. 2.10. Change in TCWV from 2008
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Precipitation anomalies in 2009, ov
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Fig. 2.18. Seasonal SCE anomalies (
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USING SI-TRACABLE GLOBAL POSITIONIN
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6) Lake levels—C. BirkettLake vol
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Fig. 2.30. (a) The daily AO index f
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(C) Carbon monoxide (CO)There has b
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Table 2.5. Mixing ratios, radiative
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the mid-1990s but has since levelle
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with all 42 glaciers observed retre
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of 0.1° and 5 days (Kaiser et al.
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Fig. 3.1. (a) Yearly mean SSTAs in
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(Fig. 3.3c). It is interesting that
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strong there, consistent with anoma
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cont'RECENT ADVANCES IN OUR UNDERST
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is to cause SST to rise if oceanic
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egions around the subtropical salin
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Fig 3.17. Principal empirical ortho
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Fig. 3.19. Daily estimates of the s
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Fig. 3.22. (top) The 2009 SSH anoma
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to update the CO 2climatology, ther
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µmol kg -1 or about half of the ac
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Fig. 3.31. (a) Average MODIS-Aqua C
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latitudes, chlorophyll and thermal
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Fig. 4.4. (a) Anomalous 850-hPa win
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(Fig. 4.6). These include four MJO
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Fig. 4.8. NOAA’s ACE index expres
Page 89 and 90: Fig. 4.14. ASO 2009: Anomalous 200-
Page 91 and 92: Fig. 4.17. The tracks of all TCs th
Page 93 and 94: Several previous studies have shown
Page 95 and 96: followed by TY Linfa and TS Nangka
Page 97 and 98: The Philippines were severely affec
Page 99 and 100: The historical SIO TC data is proba
Page 101 and 102: Fig. 4.26. Global anomalies of TCHP
Page 103 and 104: degree resolution NASA TRMM rainfal
Page 105 and 106: F i g. 4.32 . TRMM (a) mean and (b)
Page 107 and 108: THE forgotten sub-BASIN—THE centr
Page 109 and 110: 5. THE ARCTIC—J. Richter-Menge, E
Page 111 and 112: and North America (south of 55° la
Page 113 and 114: Fig. 5.8. 2007-09 Atlantic water la
Page 115 and 116: d. Sea ice cover—D. Perovich, R.
Page 117 and 118: e. Land1) Vegetation—D. A. Walker
Page 119 and 120: Fig. 5.18. Total annual river disch
Page 121 and 122: negative SCD anomalies were evident
Page 123 and 124: with records beginning in 1873, the
Page 125 and 126: (QuikSCAT, 2000-09) microwave remot
Page 127 and 128: 6. ANTARCTICAa. Overview—R. L. Fo
Page 129 and 130: (SCAR) report ‘Antarctic Climate
Page 131 and 132: these stations in April, August, an
Page 133 and 134: e. 2008-2009 Seasonal melt extent a
Page 135 and 136: positive ice-season duration anomal
Page 137 and 138: 7. REGIONAL CLIMATESa. Introduction
Page 139: first half of the year (January-Jun
Page 143 and 144: California began the year with mode
Page 145 and 146: The first drought occurred in March
Page 147 and 148: Fig. 7.8. (a) Annual mean temperatu
Page 149 and 150: Fig. 7.11. (a) Annual mean temperat
Page 151 and 152: EXTREME rainfall and the flood of t
Page 153 and 154: Fig. 7.14. Composite for standardiz
Page 155 and 156: Fig. 7.17. Daily maximum temperatur
Page 157 and 158: (ii) PrecipitationDecember to Febru
Page 159 and 160: For Zimbabwe, the rainfall season,
Page 161 and 162: Fig. 7.28. Annual mean temperature
Page 163 and 164: Fig. 7.31. Seasonal anomalies (1961
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Page 167 and 168: cold in southern and central Finlan
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Page 171 and 172: 7.32b). April was particularly mild
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Page 175 and 176: Fig. 7.39. Weather conditions in De
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Page 179 and 180: excess rainfall, while 11 subdivisi
Page 181 and 182: 4) Southwest Asia(i) Iraq—M. Roge
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Table 7.5. Maximum temperature anom
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8. SEASONAL SUMMARIES—Mike Halper
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Fig. 8.5. Jun-Aug 2009 (top) surfac
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ACKNOWLEDGMENTSIn addition to the m
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CFCCFC-11CFC-12CH 4Chl satCIIFENClC
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OAFlux Objectively Analyzed Air-Sea
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Ashok, K., S. K. Behera, S. A. Rao,
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Cangialosi, J. P., and L. A. Avila,
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Francis, J. A., W. Chan, D. J. Leat
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Hudson, J. M. G., and G. H. R. Henr
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Landsea, C. W., and W. M. Gray, 199
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Meinen, C. S., M. O. Baringer, and
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Ramaswamy, V., M. D. Schwarzkopf, W
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——, ——, T. C. Peterson, and
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Wang, L., C. Derksen, and R. Brown,
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Monthly average temperature anomali
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STATE OF THE CLIMATE IN 2009

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