Kenneth Kunkel

Kenneth Kunkel

CICS-NC
NOAA's National Climatic Data Center
Veach-Baley Federal Building
151 Patton Avenue
Asheville, NC 28801-5001
 Telephone: +1 828.257.3137
.(JavaScript must be enabled to view this email address)

Dr. Kunkel’s recent research has focused on climate variability and change, particularly related to extreme events, such as heavy precipitation, heat waves, cold waves, and winter storms. A particular focus has been the historical variations in the frequency and intensity of such extreme events extending from the late 19th Century to the present. An examination of late 19th and early 20th Century variations is important because it establishes the quasi-natural background which provides a context for interpreting recent variations and possible anthropogenic influences.

He has also engaged in the diagnostic analysis of both regional and global climate model output. This has focused on the regional fidelity of model simulations of the climate of the U.S., including such features as the North American monsoon and the lack of 20th Century warming in the central U.S.

He has developed a number of applications of climate data, including a temperature-based model that anticipates the risk of West Nile Virus infections and a soil moisture model for agricultural usage in the Midwest.

As part of his involvement in the National Climate Assessment, he led the development of a nine-part NOAA Technical Report series published in 2013, to support the development of the Third National Climate Assessment report. This series provides regionally-specific information on historical climate trends and scenarios of future climate change.

Dr. Kunkel joined CICS-NC as a Senior Scientist and Science Lead for Assessments, and, the Department of Marine, Earth and Atmospheric Sciences as a Research Professor in September 2010.

2013

Kunkel, K.E., T.R. Karl, D.R. Easterling, K. Redmond, J. Young, X. Yin, and P. Hennon, 2013: Probable maximum precipitation (PMP) and climate change.  Geophys. Res. Lett., in press.

Kunkel, K.E., T.R. Karl, H. Brooks, J. Kossin, J. Lawrimore, D. Arndt, L. Bosart, D. Changnon, S.L. Cutter, N. Doesken, K. Emanuel, P.Ya. Groisman, R.W. Katz, T. Knutson, J. O’Brien, C. J. Paciorek, T. Peterson, K. Redmond, D. Robinson, J. Trapp, R. Vose, S. Weaver, M. Wehner, K. Wolter, D. Wuebbles, 2013: Monitoring and understanding changes in extreme storms: state of knowledge. Bull. Amer. Meteor. Soc., in press.

Kunkel, K.E, L.E. Stevens, S.E. Stevens, L. Sun, E. Janssen, D. Wuebbles, J. Rennells, A. DeGaetano, and J.G. Dobson, 2013: Part 1. Climate of the Northeast U.S., NOAA Technical Report NESDIS 142-1, 80 pp.

Kunkel, K.E, L.E. Stevens, S.E. Stevens, L. Sun, E. Janssen, D. Wuebbles, C.E. Konrad II, C.M. Fuhrman, B.D. Keim, M.C. Kruk, A. Billet, H. Needham, M. Schafer, and J.G. Dobson, 2013: Part 2. Climate of the Southeast U.S., NOAA Technical Report NESDIS 142-2, 95 pp.

Kunkel, K.E, L.E. Stevens, S.E. Stevens, L. Sun, E. Janssen, D. Wuebbles, S.D. Hilberg, M.S. Timlin, L. Stoecker, N.E. Westcott, and J.G. Dobson, 2013: Part 3. Climate of the Midwest U.S., NOAA Technical Report NESDIS 142-3, 96 pp.

Kunkel, K.E, L.E. Stevens, S.E. Stevens, L. Sun, E. Janssen, D. Wuebbles, M.C. Kruk, D.P. Thomas, M. Shulski, N. Umphlett, K. Hubbard, K. Robbins, L. Romolo, A. Akyuz, T. Pathak, T. Bergantino, and J.G. Dobson, 2013: Part 4. Climate of the U.S. Great Plains, NOAA Technical Report NESDIS 142-4, 83 pp.

Kunkel, K.E, L.E. Stevens, S.E. Stevens, L. Sun, E. Janssen, D. Wuebbles, K.T. Redmond, and J.G. Dobson, 2013: Part 5. Climate of the Southwest U.S., NOAA Technical Report NESDIS 142-5, 79 pp.

Kunkel, K.E, L.E. Stevens, S.E. Stevens, L. Sun, E. Janssen, D. Wuebbles, K.T. Redmond, and J.G. Dobson, 2013: Part 6. Climate of the Northwest U.S., NOAA Technical Report NESDIS 142-6, 76 pp.

Stewart, B.C., K.E. Kunkel, L.E. Stevens, L. Sun, and J.E. Walsh, 2013: Part 7. Climate of Alaska, NOAA Technical Report NESDIS 142-7, 61 pp.

Keener, V.W., K. Hamilton, S.K. Izuka, K.E. Kunkel, L.E. Stevens, and L. Sun, 2013: Part 8. Climate of the Pacific Islands, NOAA Technical Report NESDIS 142-8, 45 pp.

Kunkel, K.E, L.E. Stevens, S.E. Stevens, L. Sun, E. Janssen, D. Wuebbles, and J.G. Dobson, 2013: Part 9. Climate of the Contiguous United States, NOAA Technical Report NESDIS 142-9, 78 pp.

2012

Kunkel, K.E., 2012: Uncertainties in Observed Changes in Climate Extremes. In Extremes in a Changing Climate – Detection, Analysis & Uncertainty. A.AghaKouchak, D. Easterling, K. Hsu, S. Shubert, and S. Sorooshian (Eds.), Springer, 423pp, 287-307.

Karl, T.R. B.E. Gleason, M.J. Menne, J.R. McMahon, R.R. Heim, Jr, M.J. Brewer, K.E. Kunkel, D.S. Arndt, J.L. Privette, J.J. Bates, P.Y. Groisman, and D.R. Easterling, 2012: U.S. temperature and drought: Recent anomalies and trends. EOS, 93, 473-474.

Kunkel, K.E., D.R. Easterling, D.A.R. Kristovich, B. Gleason, L. Stoecker, and R. Smith, 2012: Meteorological causes of the secular variations in observed extremeprecipitation events for the conterminous United States. J. Hydromet., 13, 1131-1141.

Liang, X.-Z., M. Xu, X. Yuan, T. Ling, H.I. Choi, F. Zhang, L. Chen, S. Liu, S. Su, F. Qiao, Y. He, J.X.L. Wang, K.E. Kunkel, W.Gao, E. Joseph, V. Morris, T.-W. Yu, J. Dudhia, and J. Michalakes, 2012: Regional Climate-Weather Research and Forecasting Model (CWRF). Bull. Amer. Meteor. Soc.93, 1363-1387.

Liang, X.-Z., M. Xu, W. Gao, K.R. Reddy, K.E. Kunkel, D.L. Schmoldt, and A.N. Samel, 2012: Physical modeling of U.S. cotton yields and climate stresses during 1979-2005. Agronomy Journal, 104, 675-683, doi:10.2134/agronj2011.0251.

2011

Liang, X.-Z., M. Xu, W. Gao, K.R. Reddy, K.E. Kunkel, D.L. Schmoldt, and A.N. Samel, 2011: A distributed growth model developed from GOSSYM and its parameter determination. Agronomy Journal, 104, 661-674, doi: 10.2134/agronj2011.0250.

Westcott, N.E., S.D. Hilberg, R.L. Lampman, B.W. Alto, A. Bedel, E.J. Muturi, H. Glahn, M. Baker, K.E. Kunkel, and R.J. Novak, 2011:  Predicting the seasonal shift in mosquito populations preceding the onset of the West Nile Virus in central Illinois.  Bull. Amer. Meteor. Soc., 92, 1173-1180.

2010

Kunkel, K.E., D. Easterling, D.A.R. Kristovich, B. Gleason, L. Stoecker, and R. Smith, 2010:  Recent increases in U.S. heavy precipitation associated with tropical cyclones.  Geophys. Res. Lett., 37, L24706, 4 pp., doi:10.1029/2010GL045164.

Kunkel, K.E., X.-Z. Liang, and J. Zhu, 2010:  Regional climate model projections and uncertainties of U.S. summer heat waves.  J. Climate, 23, 4447–4458.

Angel, J.R. and K. E. Kunkel, 2010: The response of Great Lakes water levels to future climate scenarios with an emphasis on Lake Michigan.  J. Great Lakes Res., 36, 51–58.

National Climate Assessment Scientific Support Activities

EXECUTIVE SUMMARY

An analysis of the physical climate of the National Climate Assessment (NCA) regions was completed, including historical trends based on NOAA climate observations and 21st Century projections based on CMIP3 and NARCCAP climate models, for use by the authors of the 2013 NCA report. Research on extreme precipitation trends identified the major meteorological phenomena responsible for observed upward trends and examined the potential effects of climate change on estimates of probable maximum precipitation.

BACKGROUND

NOAA is participating in the high-level, visible, and legally mandated National Climate Assessment (NCA) process, which will be responsive to greater emphasis on user-driven science needs under the auspices of the US Global Change Research Program (USGCRP). National climate assessments are intended to advance the understanding of climate science in the larger social, ecological, and policy systems to provide integrated analyses of impacts and vulnerability. NOAA's National Climatic Data Center (NCDC) and many parts of NOAA have provided leadership on climate assessment activities for over a decade. A renewed focus on national and regional climate assessments to support improved decision-making across the country continues to emerge. Decisions related to adaptation at all scales as well as mitigation and other climate-sensitive decisions will be supported through an assessment design that is collaborative, authoritative, responsive and transparent. NOAA is working through an interagency process and investing in partnerships across many scales to support this comprehensive assessment activity. To support these activities, CICS-NC has instituted a task group of a senior scientist, a deputy focused on coordination, an attribution support member and a DC-based staff support member. The Lead Senior Scientist provides scientific oversight for the development of NOAA’s assessment services, focusing on a contribution to the National Climate Assessment and, in support of the National Climate Assessment and in conjunction with NOAA and other agency expertise, providing scientific oversight and guidance to coordinate and implement distributed and centralized high-resolution modeling capabilities.

ACCOMPLISHMENTS

An analysis of historical climate variations and trends was completed, focused around eight U.S. regions defined for the 2013 National Climate Assessment report. This analysis examined trends in mean temperature and precipitation, metrics of extreme temperature and precipitation, freeze-free season length, and variables of more regional interest, such as lake ice in northern regions. For example, a set of very long-term precipitation-observing COOP stations was used to examine the temporal and spatial variations in number of extreme precipitation totals of 2-day duration. Time series of spatially averaged indices (Fig. 3) indicate that since 1991, all regions have experienced a greater than normal occurrence of extreme events. In the eastern regions, the recent numbers are the largest since reliable records begin (1895). In addition to the historical analysis, climate model simulations of the 21st Century for the A2 and B1 scenarios were analyzed and summarized for use by the authors of the 2013 report. The analysis examined the CMIP3 suite of global climate models, statistically downscaled versions of the CMIP3 models, and regional climate model simulations from the North American Regional Climate Change Assessment Project. Nine documents were prepared, summarizing the historical data analysis and the analysis of the climate models.

Figure 1: Time series of decadal values of an index (standardized to 1) of the number of 2-day precipitation totals exceeding a threshold for a 1 in 5-yr occurrence for 7 regions and the U.S. as a whole. This was based on an individual analysis of 930 long-term stations. Station time series of the annual number of events were gridded and then regional annual values were determined by averaging grid points within the region. Finally, the results were averaged over decadal periods.

Research on extreme precipitation examined the potential influence of water vapor changes on the observed increase in extreme precipitation. This was done by examining precipitable water values associated with extreme precipitation events for the period of 1971-2009. These precipitable water values were compared for two periods: 1971-1989 and 1990-2009. The results in Table 2 depict significant increases in the water vapor associated with extreme precipitation events in the latter period, particularly east of the Rockies.

Table 2. Differences between two periods (1990-2009 minus 1971-1989) for daily, 1-in-5yr extreme events and coincident (spatial and temporal) precipitable water values.

Region

Extreme Precipitation Frequency index Difference (%)

Precipitable Water Difference (%)

Northeast

+55**

+2

Southeast

+11*

+9***

Midwest

+21**

+6**

North Great Plains

+18*

+16***

South Great Plains

+15

+8***

Northwest

+36*

+4

Southwest

+36*

-4

*Significant at 0.10 level
**Significant at 0.05 level
***Significant at 0.01 level

The potential effect of climate change on future values of probable maximum precipitation was examined by looking at simulated future changes in maximum precipitation water. Climate model simulations indicate a substantial increase in water vapor concentrations during the 21st Century. There is high confidence in this model outcome because the imbalance in the radiative energy budget arising from an increase in greenhouse gases will almost surely be manifested in an increase in ocean heat content. This in turn will lead to an increase in near-surface atmospheric water vapor concentrations over the oceans. The model simulations indicate that the changes in maximum water vapor concentrations, which are a principal input to Potential Maximum Precipitation (PMP) estimation techniques, will change by an amount similar to mean water vapor changes, and ultimately to an accelerated water cycle with heavier extreme rains. Changes in other factors used as inputs to PMP are not clear, neither from theoretical considerations nor from analyses of climate model simulations. In the absence of any basis for adjusting these factors, the best assumption is that these will not change in the future. This leads to the conclusion that the most scientifically sound projection is that probable maximum precipitation values will increase in the future.

Research was conducted to determine the meteorological phenomena associated with the increase in extreme precipitation events. Daily extreme precipitation events, exceeding a threshold for a 1 in 5 yr occurrence, were identified from a network of 935 cooperative observer stations for the period of 1908-2009. Each event was assigned a meteorological cause, categorized as extratropical cyclone near a front (FRT), extratropical cyclone near center of low (ETC), tropical cyclone (TC), mesoscale convective system (MCS), air mass (isolated) convection (AMC), North American Monsoon (NAM), and upslope flow (USF). The percentage of events ascribed to each cause were 54% for FRT, 24% for ETC, 13% for TC, 5% for MCS, 3% for NAM, 1% for AMC, and 0.1% for USF. On a national scale, there are upward trends in events associated with fronts and tropical cyclones, but no trends for other meteorological causes. On a regional scale, statistically significant upward trends in the frontal category are found in five of the nine regions.

PLANNED WORK

  • Contribute to the writing of the 2013 National Climate Assessment Report.
  • Revised regional climate descriptions in response to review comments
  • Conduct an analysis of CMIP5 climate model simulations based on needs of the national climate assessment
  • Complete journal article on effects of climate change on probable maximum precipitation
  • Complete analysis of the atmospheric water vapor environment associated with the upward trend in extreme precipitation events and submit journal article on results

PUBLICATIONS - Peer Reviewed

Kunkel, K.E., T.R. Karl, H. Brooks, J. Kossin, J. Lawrimore, D. Arndt, L. Bosart, D. Changnon, S.L. Cutter, N. Doesken, K. Emanuel, P.Ya. Groisman, R.W. Katz, T. Knutson, J. O’Brien, C. J. Paciorek, T. Peterson, K. Redmond, D. Robinson, J. Trapp, R. Vose, S. Weaver, M. Wehner, K. Wolter, D. Wuebbles, (in review) Monitoring and understanding changes in extreme storm statistics: state of knowledge. Bull. Amer. Meteor. Soc.

Liang, X.-Z., M. Xu, X. Yuan, T. Ling, H.I. Choi, F. Zhang, L. Chen, S. Liu, S. Su, F. Qiao, Y. He, J.X.L. Wang, K.E. Kunkel, W.Gao, E. Joseph, V. Morris, T.-W. Yu, J. Dudhia, and J. Michalakes, 2012: Regional Climate-Weather Research and Forecasting Model (CWRF). Bull. Amer. Meteor. Soc. (accepted)

Liang, X.-Z., M. Xu, W. Gao, K.R. Reddy, K.E. Kunkel, D.L. Schmoldt, and A.N. Samel (in press) Development of a distributed cotton growth model and its parameter determination over the United States. Agronomy Journal.

Liang, X.-Z., M. Xu, W. Gao, K.R. Reddy, K.E. Kunkel, D.L. Schmoldt, and A.N. Samel (in press) Physical modeling of U.S. cotton yields and climate stresses during 1979-2005. Agronomy Journal.

Kunkel, K.E., D.R. Easterling, D.A.R. Kristovich, B. Gleason, L. Stoecker, and R. Smith (in press) Meteorological causes of the secular variations in observed extreme precipitation events for the conterminous United States. J. Hydromet.

Westcott, N.E., S.D. Hilberg, R.L. Lampman, B.W. Alto, A. Bedel, E.J. Muturi, H. Glahn, M. Baker, K.E. Kunkel, and R.J. Novak, 2011: Predicting the seasonal shift in mosquito populations preceding the onset of the West Nile Virus in central Illinois. Bull. Amer. Meteor. Soc., 92, 1173-1180.

PUBLICATIONS - Non-peer reviewed

Kunkel, K.E., L. Stevens, S.E. Stevens, E. Janssen, and K.T. Redmond (in review) Climate of the Northwest U.S., prepared for the National Climate Assessment Development and Advisory Committee.

Kunkel, K.E., L. Stevens, S.E. Stevens, E. Janssen, and K.T. Redmond (in review) Climate of the Southwest U.S., prepared for the National Climate Assessment Development and Advisory Committee.

Kunkel, K.E., L. Stevens, S.E. Stevens, E. Janssen, C.E. Konrad II, C.M. Fuhrmann, B.D. Keim, M.C. Kruk, A. Billot, H. Needham, and M. Shafer (in review) Climate of the Southeast U.S., prepared for the National Climate Assessment Development and Advisory Committee.

Kunkel, K.E., L. Stevens, S.E. Stevens, E. Janssen, S. Hilberg, M. Timlin, L. Stoecker, and N. Westcott (in review) Climate of the Midwest U.S., prepared for the National Climate Assessment Development and Advisory Committee.

Kunkel, K.E., L. Stevens, S.E. Stevens, M.C. Kruk, D.P. Thomas, E. Janssen, K.G. Hubbard, M.D. Shulski, N.A. Umphlett, K. Robbins, L. Romolo, A. Akyuz, T.B. Pathak, and T.R. Bergantino (in review) Climate of the U.S. Great Plains, prepared for the National Climate Assessment Development and Advisory Committee.

Kunkel, K.E., L. Stevens, S.E. Stevens, and E. Janssen (in review) Climate of the Contiguous United States, prepared for the National Climate Assessment Development and Advisory Committee.

Kunkel, K.E., L. Stevens, S.E. Stevens, E. Janssen, J. Rennells and A. DeGaetano (in review) Climate of the Northeast U.S., prepared for the National Climate Assessment Development and Advisory Committee.

Stewart, B.C., and J.E. Walsh, K.E. Kunkel, and L.E. Stevens (in review) Climate of Alaska, prepared for the National Climate Assessment Development and Advisory Committee.

Victoria W. Keener, V.W. and K. Hamilton, and S.K. Izuka, K.E. Kunkel, K.E., and L. Stevens (in review) Climate of the Pacific Islands, prepared for the National Climate Assessment Development and Advisory Committee.

PRESENTATIONS

  • Farrell, S.L. (2011b), AOSC 401: Global Environment, Aspects of the Cryosphere: Sea Ice and Snow, Guest Lecture for Prof. Zhanqing Li, Dept. of Atmospheric and Oceanic Science, University of Maryland, College Park, MD, 1 April 2011.
  • Kunkel, K.E. (2012), Recent Weather in the United States: Are Extremes Becoming More Prevalent?, invited talk, Monsanto Corp., St. Louis, MO, 13 February, 2012.
  • Kunkel, K.E. (2012), Climate Change Impacts on Probable Maximum Precipitation, 2012 Annual Meeting of the American Meteorological Society, New Orleans, LA, 25 January, 2012.
  • Kunkel, K.E. (2012), Overview of previous work (SAP 3.3), and workshop challenge, invited talk, Forum on Trends in Extreme Winds, Waves, and Extratropical Storms along the Coasts, Asheville, NC, 11 January, 2012
  • Kunkel, K.E. (2011), Observed Trends in Temperature and Precipitation Extremes, invited talk, 2011 Fall AGU Meeting, San Francisco, CA, 6 December, 2011.
  • Kunkel, K.E. (2011), Climate Change Impacts on Probable Maximum Precipitation, invited talk, 2011 Fall AGU Meeting, San Francisco, CA, 5 December, 2011.
  • Kunkel, K.E. (2011), Climate Scenarios Update, invited talk, meeting of the National Climate Assessment Development and Advisory Committee, Boulder, CO, 15 November, 2011.
  • Kunkel, K.E. (2011), Northeast Regional Climatology and Outlook, invited talk, Northeast Regional Assessment Workshop, New York City, NY, 17 November, 2011.
  • Kunkel, K.E. (2011), Temperature Extremes, invited talk, Workshop: Trends and Causes of Observed Changes in Heat and Cold Waves as well as Drought, Asheville, NC, 8 November, 2011.
  • Kunkel, K.E. (2011), Past Assessment, invited talk, Workshop: Trends and Causes of Observed Changes in Heat and Cold Waves as well as Drought, Asheville, NC, 8 November, 2011.
  • Kunkel, K.E. (2011), Meteorological Causes of Extreme Precipitation Trends in the U.S., World Climate Research Programme Open Science Conference, Denver, CO, 24 October, 2011.
  • Kunkel, K.E. (2011), Extreme Precipitation, NCDC Seminar, Asheville, 17 October, 2011.
  • Kunkel, K.E. (2011), Extreme Precipitation, invited talk, NOAA Climate Board, Washington, DC, 14 October, 2011.
  • Kunkel, K.E. (2011), Southeast Regional Outlook, invited talk, Southeast Regional Assessment Workshop, Atlanta, GA, 26 September, 2011.
  • Kunkel, K.E. (2011), Southwest Regional Climatology and Outlook, invited talk, Southwest Regional Assessment Workshop, Boulder, CO, 1 August, 2011.
  • Kunkel, K.E. (2011), Workshop Challenge and Background, Workshop on Monitoring Changes in Extreme Storms Statistics: State of Knowledge, Asheville, NC, 25 July, 2011.
  • Kunkel, K.E. (2011), Precipitation Extremes-Mechanistic Perspective, Workshop on Monitoring Changes in Extreme Storms Statistics: State of Knowledge, Asheville, NC, 25 July, 2011.
  • Kunkel, K.E. (2011), State Climatologist Contributions to the National Climate Assessment, invited talk, Annual Meeting of the American Association of State Climatologists, Asheville, NC, 21 July, 2011.
  • Kunkel, K.E. (2011), Potential Impacts of Climate Changes on Estimates of Probable Maximum Precipitation, Practical Solutions for a Warming World: AMS Conference on Climate Adaptation, Asheville, NC, 19 July, 2011.
  • Kunkel, K.E. (2011), “Trends in Extreme Snowfall Seasons”, invited talk, NOAA/FEMA Snow Workshop, Estes Park, CO, May 26, 2011.
  • Kunkel, K.E. (2011), National Climate Assessment and NARCCAP, invited talk, NARCCAP Users Workshop, Boulder, CO, 7 April, 2011.
  • Kunkel, K.E. (2011), Development of Regional Climate Information for the National Climate Assessment, invited talk, inaugural meeting of the National Climate Assessment Development and Advisory Committee, Washington, DC, 5 April, 2011.

OTHER

None


Trends in Extratropical Cyclone Occurrence

Task Leader Kenneth Kunkel
Task Code
Date awarded 07/01/2011
Percent contribution to CICS Themes Theme 1: 0%; Theme 2: 0%; Theme 3: 100%
Percent contribution to NOAA Goals Goal 1: 100%

EXECUTIVE SUMMARY

This project is investigating the nature of changes in extratropical cyclone (ETC) occurrence using a new reanalysis data set that extends back into the late 19th Century. Preliminary results point to some significant shifts in the spatial distribution and frequency of ETCs from the late 19th to the early 21st Century in the Northern Hemisphere. Most importantly, trends in ETC activity computed over more than 100 years are in some cases opposite in sign to those computed since 1950. The ratio of the number of high latitude to mid latitude ETCs was higher in the late 19th/early 20th Centuries; on the surface, this implies a shift in the mean track of ETCs to the south during the latter two-thirds of the 20th Century. Indeed, the mid-latitudes of North America and the Atlantic became more active after the 1930s. At the same time, at high latitudes there was a change to higher activity in the eastern Hemisphere and lesser activity in the western Hemisphere. These shifts indicate a need to rethink probable weather patterns in climate change scenarios.

BACKGROUND

ETCs are large-scale, non-tropical low pressure storm systems that typically develop along a frontal boundary between air masses of contrasting temperature. The ETC is the principal atmospheric phenomenon through which sensible and latent heat fluxes are exchanged between the subtropical and polar regions. These large-scale cyclonic storms are the major feature of mid-latitude weather during the colder times of the year and often have severe weather associated with them. These storms can produce large snowfall amounts that, together with high winds, result in blizzard conditions, large waves leading to coastal erosion, and severe convective events with lightning and tornadoes. In fact, these storms (or their absence in the case of drought) are responsible for many of the extreme weather types experienced at mid- and high-latitudes. ETCs are ubiquitous throughout the year, but tend to be stronger and located more equatorward in the cold season. Future changes in extreme weather in mid to high latitudes will likely involve changes in the frequency, intensity, and tracks of ETCs.

A number of recent studies focused on the Northern Hemisphere have documented a significant poleward shift of the storm track in both the Pacific and Atlantic ocean basins, a decrease in ETC frequency in mid-latitudes, and a corresponding increase in ETC activity at higher latitudes for the latter half of the 20th century. Future climate warming may lead to a decrease in polar low activity. A new analysis of surface pressure data has extended the availability of pressure field data from the mid-20th century as used in previous studies, back to the late 19th Century. We have used this new 20th Century Reanalysis (20CR) data set to extend the analysis of ETC occurrence in the Northern Hemisphere to the period 1871-2007.

We examined the 20CR record (Fig. 1), restricting the analysis to significant long-lived ETCs (storms lasting at least 72h and travelling at least 1000 km), and found that a different picture emerges. There is an overall upward trend in ETC occurrence in mid latitudes (30°-60°N), but no trend for high latitude (60°-90°N) ETCs. Further examination of the ETC counts over time reveals that in the late 19th and early 20th Century, high latitude ETC occurrence was similar to the latter part of the 20th Century (Fig. 1). In contrast, mid-latitude ETC activity in the late 19th/early 20th Century was considerably lower than in the recent period.

Figure 1. Northern Hemisphere ETC Activity. Thin solid line: normalized mean ETC activity for polar (60-90°) and mid-latitude (30-60°) bands, upper and lower plots respectively. Shaded bars indicate the ETC activity for the second smallest and second largest of the 56 ensemble members. Heavy straight lines indicate the least squares fit from 1871-2007 and 1950-2007, respectively. Statistically significant slopes (95% confidence interval) are plotted with a red line

ACCOMPLISHMENTS

We examined the 20CR record (Fig. 1), restricting the analysis to significant long-lived ETCs (storms lasting at least 72h and travelling at least 1000 km), and found that a different picture emerges. There is an overall upward trend in ETC occurrence in mid latitudes (30°-60°N), but no trend for high latitude (60°-90°N) ETCs. Further examination of the ETC counts over time reveals that in the late 19th and early 20th Century, high latitude ETC occurrence was similar to the latter part of the 20th Century (Fig. 1). In contrast, mid-latitude ETC activity in the late 19th/early 20th Century was considerably lower than in the recent period

PLANNED WORK

  • Perform sensitivity analyses to determine the extent to which the changing spatial density of surface pressure data affects the trend results. Of particular interest is whether the sparse density of observations in the late 19th and early 20th Centuries in the North Pacific result in high or low biases in the number of ETCs in that region.

PUBLICATIONS

None

PRESENTATIONS

“20th Century Trends in Northern Hemisphere Extratropical Cyclone Occurrence”, World Climate Research Programme Open Science Conference, Denver, CO, October 2011.

OTHER

None