Topic 5.1 Climate Change and Tropical Cyclones

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1 Topic 5.1 Climate Change and Tropical Cyclones Rapporteurs: John McBride, Kevin Walsh Working Group: Masato Sugi, T- C Lee, Thomas Knutson, Suzana Camargo, Kevin Tory, S. Balachandran. ConsultaDon and valuable input: Hurricane Working Group of U.S. CLIVAR WMO Expert Team on Climate Change Impacts on Tropical Cyclones And Topic Chair :Adam Sobel Presenter: John McBride, Meteorological Service Singapore

2 IPCC 5 th Assessment: Working Group 1 Report: Christensen et al. (2013) Change in TC over (A1B scenario)

4 Category 4-5 TC Frequency Changes Numbers per 10years in 5ºx5º grid box Ensemble runs 60km resolution, with bias correction ObservaDon (BEST TRACK) Present (11 members) Future (29 members) Changes (Future- Present) Number of Cat 4-5 TCs generally increases in most regions, except for south- western part of WNP and near Australia, and ENP, Caribbean Sea and Gulf of Mexico. Sugi et al. (2014) AOGS

5 Topic 5.1 Climate Change and Tropical Cyclones Rapporteurs: John McBride, Kevin Walsh Working Group: Masato Sugi, T- C Lee, Thomas Knutson, Suzana Camargo, Kevin Tory, S. Balachandran. ConsultaDon and valuable input: Hurricane Working Group of U.S. CLIVAR WMO Expert Team on Climate Change Impacts on Tropical Cyclones And Topic Chair :Adam Sobel Presenter: John McBride, Meteorological Service Singapore

6 WG Report 5.1 Detailed literature review and discussion Looked at papers and developments since previous IWTC (2010). This coincided closely with WWRP Expert Team Review: Knutson et al., Nature Geoscience Current Report extensive literature review References and discusses 108 journal papers on tropical cyclones and climate published since 2010 Done by the Working group, but wridng effort led by Kevin Walsh

7 5.1.0 IntroducDon ObservaQons of Tropical Cyclones Paleotempestology ObservaDons: Historical and satellite era a) Global ObservaDons b) Western North Pacific c) North AtlanDc d) North Indian e) South Indian and South Pacific ENSO, Tropical Cyclones and Climate Change RelaDons between tropcial cyclone formadon and climate TheoreDcal RelaDonships between climate and intensity

8 ProjecQon of Future TC Climatology TC numbers and Occurrence TC Intensity Air- sea interacdons TC rainfall and other impacts Modelling Issues

9 5.1.3 Research Topics for the future DetecDon methods as a source of uncertainty Lack of a climate theory of tropical cyclone formadon Confidence in detecdon and adribudon of observed changes in tropical cyclones to date Impact of uncertainty in future projecdons of large- scale climate fields Correct simuladon of tropical cyclone frequency response in high resoludon climate models Correct simuladon of tropical cyclone intensity response in high resoludon climate models

10 Future projecqons of storm surge Changes in storm surges due to tropical cyclones will be caused by a combinaqon of sea level rise and changes in tropical cyclone climatology (e.g. Lin et al. 2012). Woodruff et al. (2013) review this topic, nodng that projecdons of sea level rise are more confident than projecdons of changes in tropical cyclones. In some locadons, sea level rise may dominate the changes in storm surge climatology (e.g. McInnes et al. 2014).

11 Lin, Emanuel, Oppenheimer, Vanmarcke (2012). CalculaDons of storm Dde (surge plus Dde) return levels for the badery New York, using GCMs, generadng synthedc tropical cyclones (Emanuel et al, BAMS 2006) and storm surge model (SLOSH) Black present climate, blue IPCC A1B climate, red IPCC AiB with increases in radius of max wind and outer storm radius (to increase surge)

12 Same as previous figure, but with 1 metre sea level rise added in (flood level) Black line current climate is the same as previous figure.

13 Woodruffe, Irish, Camargo: Nature 2013: Coastal flooding by tropical cyclones and sea level rise.

14 Direct detecdon of tropical cyclone acdvity from climate models (CMIP5)

15 OWZP (Okubo- Weiss- Zeta- Parameter) is a new detecdon method Developed by Kevin Tory and coauthors: Series of papers in Atmospheric Chemistry and Physics (Tory et al, 2013a) and in Journal of Climate (Tory et al, 2013b, c, d) The name comes from the Okubo- Weiss parameter from studies of 2- dimensional flows and 2- dimensional turbulence. The OW parameter measures the existence of a separate vortex, or rotaqonally dominated flow regions. Zeta incorporates the absolute vordcity. Key hypothesis is that all tropical cyclone precursors contain enhanced values of OWZ on a scale resolved by climate models (500 to 1000 km)

16 Detections for individual year cyclones in ERA- Interim analyses South Pacific South Indian North Indian North West Pacific North East Pacific North AtlanQc

17 Tory et al CMIP- 5 Study Applied OWZP algorithm to 13 CMIP- 5 models Historic run (forced by observed greenhouse gases and volcano acdvity) to see ability to reproduce current Tropical cyclone climatology Future climate (high emissions scenario) rcp8.5 to determine model projecqons

18 Of the 13 models, 8 reproduce current climatology to within +/- 50% Data (Best Tracks) High resolution model CNMR- CM5

19 Data Best Track Climate model Historic run Climate model Future climate High emission scenario Rcp 8.5

20 Results: The first three papers published on global tropical cyclone projecdons from CMIP- 5 Our paper, Tory Chand, McBride, Yeh, Dare, J Climate CMIP- 5 results same as CMIP- 3.. ReducQon in global frequency consistent across CMIP- 5 models Emanuel, PNAS 2013, downscale model (runs idealised dynamical TC model offline from CMIP- 5 model fields reports global increase in TC frequency (opposite to his CMIP- 3 results) Camargo, J Climate 2013,. Direct detecdon technique, 14 CMIP- 5 models. Found all models badly underesdmate cyclone frequency in current climate. Found no robust signal across CMIP- 5 models in global and regional changes in TC acqvity for future scenarios

21 IPCC-AR5 (2013)

22 More TCs in a Cooler Climate SST frequency distribudon at the Dme and locadon of TC genesis Annual frequency OBS observaqon HPA Present M4K 4K- cooler P4K 4K- warmer C SST Sugi et al. (2014) AOGS

23 InvesQgaQons of reason for decrease in frequency of TC s in a warmer climate: a) Decreased upward mass flux, associated with slowing of decrease in intensity of tropical circuladon Held and Zhao 2011; Sugi et al. 2012; Zhao et al b) Decrease in mid- level moisture saturadon deficit Emanuel et al. 2008; Rappin et al. 2010)

24 Use Of Tropical Cyclone Genesis Indices (TCGI) descendent of work of Gray 1968, Emanuel- Nolan * To downscale from Global coupled models * To use as a theoredcal framework to understand changes in tropical cyclone frequency

25 Camargo et al. J. Clim 2015 (In Press) Genesis Index (Poisson regression on large scale parameters, reladve vordcity, SST or MPI, verdcal shear etc) Maps of Genesis Index TC cliamtology from HIRAM model, NCEP reanalyses and ERA- 40

27 Camargo et al 2015: some TCGIs which perform well in the present climate do not accurately reproduce the simulated future decrease in TC frequency. This decrease is captured when the humidity predictor is the column saturaqon deficit rather than relaqve humidity. Using saturadon deficit with reladve SST as the other thermodynamic predictor over- predicts the TC frequency decrease, While using potendal intensity in place of reladve SST as the other thermodynamic predictor gives a good predicdon of the decrease s magnitude.

28 WG Report 5.1 Detailed literature review and discussion Looked at papers and developments since previous IWTC (2010). This coincided closely with WWRP Expert Team Review: Knutson et al., Nature Geoscience Current Report extensive literature review References and discusses 108 journal papers on tropical cyclones and climate published since 2010 Done by the Working group, but wridng effort led by Kevin Walsh

29 108 papers. Many interesqng developments The high divergence in model projecdons for individual basins Consistent projecdons of global decrease in cyclone frequency Importance of addressing sea level rise storm surge flooding return periods for 10 to 100 years dominated by rise in sea level Direct detecdons. Tory et al work. DetecDon based on large scale condidons for cyclone genesis (Marsupial pouch paradigm) Three CMIP 5 papers with three different results InnovaDve work with Tropical Cyclone Genesis Indices (role of mid level saturadon deficit) RecommendaQons Topic chair will address

4. Climatic changes. Past variability Future evolution

4. Climatic changes. Past variability Future evolution 4. Climatic changes Past variability Future evolution TROPICAL CYCLONES and CLIMATE How TCs have varied during recent and distant past? How will TC activity vary in the future? 2 CURRENT CLIMATE : how