Climate Change and Southern Hemisphere Tropical Cyclones International Initiative: Twenty Years of Successful Regional Cooperation

Abstract

Tropical cyclones (TCs) are the most dangerous weather phenomena to regularly affect countries in the Southern Hemisphere (SH). Historical records demonstrate significant inter-annual variability in TC frequency and spatial distribution of cyclone tracks; consequently, the year-to-year impact of TCs on countries varies. The El Niño-Southern Oscillation is one of the key global climate drivers which affects TC occurrences in the SH; however, there are other important large-scale environmental factors which contribute to inter-annual and intra-annual TC variability. Additionally, climate is changing on a global scale and it is important to understand how a warmer climate may affect TC activity. Since 1999 several academic, research and operational agencies from countries of the SH combined their efforts in improving our understanding of changes in regional TC activity due to natural variability and climate change, and established the “Climate Change and Southern Hemisphere Tropical Cyclones” International Initiative. The Initiative’s overarching strategy is to provide science-based information for enhancing TC early warning systems and assist with decision making in climate change adaptation and disaster risk reduction. As a result of these multi-national efforts, the first consolidated regional database of historical TC data for the SH (satellite-era, i.e. 1970 to present) was created; influence of global climate drivers on TC variability was investigated; a comprehensive TC climatology for the SH and skillful TC seasonal prediction models were developed. This publication highlights major achievements of this International Initiative over the past two decades. It also includes a brief description of the Tropical Cyclone Data Portal helping readers to learn quickly how to use this web-based information tool for examining historical TC activity over the regions of interests.

Appendices

Afterword

In December 2012, I was working in Fiji with colleagues from RSMC Nadi on revision of TC historical data. Since 1999, when the “Climate Change and Southern Hemisphere Tropical Cyclones” International Initiative was established meteorologists from Fiji were among active supporters of and contributors to this Initiative. High quality of observational data is vital for deriving plausible concussions about past TC activity and we dedicated substantial efforts preparing the SH TC data archive over the years of the Initiative.

December is the second month of a TC season in the SH and we already expected that at least one cyclone will be forming in the South Pacific in that month. When I came to RSMC Nadi’s operational division on 10 December 2012 first that I heard from my colleagues was about tropical depression which according to numerical weather prediction models will develop to a stage of tropical cyclone soon. ‘Tropical cyclone bench’ was activated and for the next ten days we closely monitored formation and development of this system which became the first cyclone in the 2012–13 South Pacific cyclone season.

The system was named as a tropical cyclone Evan on 11 December 2012 and over duration of its life cycle affected Western Samoa, American Samoa, Fiji, Tonga, Wallis and Futuna causing severe destructions in the island countries. We were looking at the historical data and it was fear that Evan’s impact may be as bad as impact of 1993 tropical cyclone Kina—one of the deadliest cyclones to affect Fiji in recent history with 23 lives lost. It was expected that Evan will arrive into the Fiji waters around 17 December 2012 as a category 4 or possibly category 5, severe tropical cyclone.

In preparation for the cyclone’s impact on Fiji, colleagues from RSMC Nadi regularly issued Media Releases sending a clear message—“All communities in Fiji should be prepared now and act responsibly, to avoid unnecessary loss of lives and property”. Fijian authorities took fast and effective actions evacuating residents from areas which could be potentially affected as well as tourists from resorts located in small islands. It was reported that about 8000 people found refuge from Evan in emergency shelters. Such actions were highly efficient and as a result there were no fatalities associated with cyclone Evan in Fiji.

On Monday, 17 December Evan started to affect Viti Levu, the largest island in Fiji. The cyclone was moving to the west of the island with an eye wall (area of a cyclone with most damaging winds) passing over the coastal areas of Viti Levu. It was the most exciting 24 h for a scientist who spent 30 years observing cyclones with satellite instruments, flying around cyclones in the Pacific Ocean on board of Ilyushin-18 aircraft-laboratory and examining historical cyclone data from all regions of the Southern Hemisphere. It was ‘my day’—to closely observe increasing strength of winds and intensity of rain when Evan was approaching Nadi, to feel hurricane for real, to witness its power.

By mid-day wind became stronger and firstly branches of trees started to move, and then whole trees came in motion; wind speed was increasing with time and small branches, and then larger branches were broken. Listening to sound of roaring winds, I was watching how leaves striped from palms and broken branches of flame and umbrella trees were flying around; from time to time I heard that broken branches and flying debris were hitting the roof and walls. Sometime these sounds were so loud that I was thinking—is this building strong enough to withstand fury of the cyclone?

Winds and rain further increased and by the evening I observed very widespread damage to vegetation with some trees uprooted as well as roofs damaged and windows broken. By about 9 pm winds reached the maximum strength of about 185 km/h and Evan’s damaging impact on Viti Levu continued through the night.

In the morning of 18 December Evan moved further south-west leaving devastated Viti Levu behind. The cyclone caused severe damage to vegetation, structural damage to buildings and infrastructure and recovery operations begun immediately. Once again, measures undertaken by the authorities were efficient, main roads were cleared from fallen trees and power supply was restored in the next few days.

Yes, living through a cyclone is a life time experience. After researching cyclones for decades, analysing changes in their geographic distribution, evaluating trends in cyclone occurrences and estimating their power, I experienced power of a cyclone and its ferocity together with thousands of Fijians who live through cyclones year after year. This experience vividly demonstrated to me vital importance of assistance which the ‘Climate Change and Southern Hemisphere Tropical Cyclones’ International Initiative provides to people living in small island countries.

Appendix: Southern Hemisphere Tropical Cyclones Data Portal

Introduction

As part of the “Climate Change and Southern Hemisphere Tropical Cyclones” International Initiative, the first consolidated regional database of historical tropical cyclone (TC) data for the Southern Hemisphere (SH) (satellite-era, i.e. 1970 to present) was created. Extending the Initiative to the Western North Pacific Ocean (WNPO), TC best track data from the Regional Specialised Meteorological Centre (RSMC) Tokyo, Japan were also added to the archive of historical data. To display TC best tracks and analyse TC spatial and temporal variability in the SH and the WNPO, the Tropical Cyclone Data Portal has been created. A detailed description of the Portal is presented here, helping readers to learn quickly how to use this web-based information tool for examining historical TC activity over the regions of interests.

The “Climate Change and Southern Hemisphere Tropical Cyclones” International Initiative has been established in 1999 aiming to improving our understanding of changes in regional tropical cyclone (TC) activity due to natural variability and climate change. During twenty years of productive cooperation among 13 organizations from 8 counties in the Asia-Pacific Region, the Initiative produced significant results which include creation of the first consolidated regional database of historical TC data for the Southern Hemisphere (SH) for satellite-era (i.e. 1970 to present). The Initiative was growing over the years extending to the Western North Pacific Ocean (WNPO). As a result, TC best track data from the Regional Specialised Meteorological Centre (RSMC) Tokyo, Japan were also added to the archive of historical data. To display TC best tracks and analyse TC spatial and temporal variability in the SH and the WNPO, the Tropical Cyclone Data Portal has been created. Here, a detailed description of the Portal is presented, helping readers to learn quickly how to use this web-based information tool for examining historical TC activity over the regions of interests.

Tropical Cyclone Data Portal

A state-of-the-art Tropical Cyclone Data Portal is a specialised web-based information tool for examining historical TC activity over the regions of interests. The Portal allows to disseminate historical TC data, visualise and analyse TC tracks in the SH and the WNPO. The Portal was developed using OpenLayers platform (Kuleshov et al. 2013) and its functionality includes dynamic map navigation, presenting detailed information for a selected region and the display of changes in TC intensity over the lifetime of a cyclone.

The SH Portal displays TC best track data from the SH TC archive which currently consists of the data from the 1969/1970 TC season to present. Similar web-based information tool has been developed for the WNPO to display TC best track data prepared by RSMC Tokyo from 1970 to present. While the same functionality is implemented in both portals there are some features specific to each portal due to differences in seasonal TC activity in the Southern and Northern Hemispheres which will be outlined here.

Detailed description the Portal’s functionality is presented below helping readers to learn quickly how to use this specialised web-based information tool to examine historical TC activity. Note that the web-browsers Mozilla Firefox and Google Chrome are preferable for using the portals, but others, such as Internet Explorer, are supported.

Navigating a Map

Zooming in and out: Click ‘+’ or ‘−’ buttons of the navigation tool at the top left corner of the map (Fig. 9) to zoom in or to zoom out, respectively. Alternatively, users can zoom using the mouse scroll wheel or by holding the SHIFT key whilst selecting an area by dragging the mouse over the map. Users can zoom to eight different map scales. The scale is shown in kilometres (km) and nautical miles (nmi) on the lower left side of the map. Clicking on ‘home’ button will zoom out bringing the map back to initial view.

Fig. 9

Initial view of the tropical cyclone data portals for the Southern Hemisphere

Panning the map area: Users can navigate by clicking (with left mouse button) and dragging the map with the mouse.

Selecting a Time Period

Click on the ‘Tracks’ tab on the top right of the screen for selecting a time period under ‘when’ option. Select a single season by clicking on a black arrow (drop down menu will appear) and then selecting a season from the menu (e.g. 1971/1972, Fig. 10). In the SH TC data portal, each cyclone season is listed using two years (e.g. 1971/1972, Fig. 10) because cyclones in the SH occur in the austral summer and a cyclone season in the SH typically lasts from November to April. In the WNPO TC Data Portal each cyclone season is listed using one year (e.g. 1971). In this region TCs occur during all months, with a minimum in February and March and a peak in September.

Fig. 10

Selecting a time period for a single season

Select a range of seasons checking ‘multi-season’ box by clicking with left mouse button, selecting the first season from drop down menu, then holding SHIFT key and selecting the last season (e.g. seasons from 2008/2009 to 2010/2011, Fig. 11). This option allows users to select a range of consecutive seasons. If using Internet Explorer, try to avoid selecting a large range of seasons as this may significantly slow down the responsiveness of the application.

Fig. 11

Selecting a time period for a range of seasons

There is an additional option for selecting a time period which provides users with various sets of pre-selected seasons. Clicking on a black arrow under ‘pre-sets’ brings the drop down menu with the following options: ‘all’, ‘latest’, ‘El Niño’, ‘La Niña’ and ‘Neutral’ (Fig. 12). From the list users can select ‘all’ to display all tracks of TCs available from the archives, ‘latest’—to display TC tracks for the latest available data, and ‘El Niño’, ‘La Niña’ and ‘Neutral’—to display TC tracks during three different phases of ENSO. For example, clicking on ‘El Niño’ option (Fig. 12) will automatically select those TC seasons when the ENSO was in its warm phase.

Fig. 12

Selecting a time period for a pre-selected range of seasons

After selection is completed, to display TC tracks on the map for the selected time period (a single season, a range of consecutive seasons or a pre-selected set of seasons), click on ‘Search’ button.

Selecting a Specific Location

Click on the ‘Tracks’ tab and check ‘where’ box. From drop down menu, four options to select a specific location are available: ‘Place name’, ‘Coordinates’, ‘Exclusive Economic Zone’ and ‘Draw area of interest’ (Fig. 13). Selecting one of the options allows users to examine TC activity with relation to a specific location (option 1—place name from a list of selected locations and option 2—any location specified by its geographic coordinates) or over a specific area (option 3—country’s Exclusive Economic Zone and option 4—area of interest of any shape which can be drawn by users). Details are given below.

Fig. 13

Selecting a specific location

For option 1 (‘Place name’), select a place name from the drop down menu (e.g. Darwin, Australia; Fig. 14). Eighty eight places from 13 countries in the SH and 10 places from 5 countries in the WNPO are listed. TC activity can be examined over a circular area centred on a selected place with a specified radius of 50, 100, 200, 300, 400 or 500 km. After selecting the place and the radius, click on ‘Search’ button to display TC tracks on the map for the selected time period. In Fig. 14, an example of track of TC Tracy which passed through a circular area with a 50 km radius centred on Darwin, Australia during 1974/1975 season is presented.

Fig. 14

Selecting a specific location using ‘Place name’ option; track of TC Tracy is displayed

If a place of interest can’t be selected from the drop down menu, option 2 (‘Coordinates’) can be used. Coordinates of a place can be entered manually in ‘latitude’ and ‘longitude’ boxes. Alternatively, click on the map to obtain coordinates. Note a minus sign which should be entered to specify a latitude in the SH; for the Northern Hemisphere, a latitude is specified with a plus sign. To specify a longitude, use a plus sing for the Eastern Hemisphere and a minus sign for the Western Hemisphere (see an example of TC tracks which affected Samoa, 13° S–172° E, in 2012/2013 TC season, Fig. 15).

Fig. 15

Selecting a specific location using ‘Coordinates’ option; tracks of TCs Evan and Garry in the vicinity of Samoa (2012/2013 TC season) are displayed

An option to examine TC activity over a country’s Exclusive Economic Zone is incorporated in the portal (Fig. 16). Select the country from drop down menu (e.g. Fiji) and click on ‘Search’ button to display TC tracks on the map for the selected time period (e.g. 2009/2010 season, Fig. 16).

Fig. 16

Selecting a specific location using ‘Exclusive Economic Zone’ option; tracks of TCs Mick, Oli, Rene and Tomas which passed through Exclusive Economic Zone of Fiji during 2009/2010 season are displayed

Another useful option for examining TC activity over a specified area is implemented under ‘Draw area of interest’ portal’s functionality. Click on a map (with left mouse button) to select points which encompass an area of interest (e.g. a rectangular area of the Australian region specified as 0–40° S, 90–160° E highlighted in grey colour in Fig. 17). To specify the last point of the selected area, double click with left mouse button and then click ‘Search’ button to display TC tracks on the map for the selected time period. Users also can draw an area of any shape holding SHIFT key and whilst holding left mouse button and moving a cursor around the map to draw an area of interest. To finish drawing, both keys should be released.

Fig. 17

Selecting a specified area using ‘Draw area of interest’ option. Tracks of TCs which passed through the selected area (the Australian region) during 2010/2011 season are displayed

Finding a Cyclone Name or Intensity

The portal provides an option for users to find a specific cyclone using its name or intensity. Click on the ‘Tracks’ tab and check ‘what’ box. From the drop down menu, two options are available: ‘Pressure’ and ‘Name’ (Fig. 18). After selecting ‘Name’ option, screen will be modified and a window for entering a cyclone name will appear. Similar, if ‘Pressure’ option is selected, screen will be modified and a window for entering a specific pressure threshold will appear. To display cyclones with an entered name (or those which attained a specified intensity in terms of minimum central pressure) during a selected season or a number of seasons, click on ‘Search’ button.

Fig. 18

Selecting a cyclone name or intensity under ‘what’ option; entering cyclone name if ‘Name’ is selected; entering pressure threshold if ‘Pressure’ option is selected

Visible Cyclones

On the bottom right of screen under ‘Visible cyclones’, users will see two numbers separated with a ‘/’ symbol. These numbers indicate the part of the cyclone tracks visible on screen in respect to the number of cyclones that met the search criteria. Cyclones are grouped by TC seasons which are listed chronologically. By clicking on the name of a cyclone, a pop-up box will appear on the map containing information about the chosen cyclone, including the cyclone name, season and start and end dates and times.

Reference Layers

At the top right side of the map, click the ‘Reference layers’ tab. Users can select a different background for the map. The drop-down menu provides three options: ‘Plain’, ‘Exclusive Economic Zones’ and ‘Elevation and Bathymetry’. After selecting one of these options, the map will be redrawn with the chosen background. A colour key in the ‘Reference layers’ tab provides information for interpreting each background.

An example of a track of TC Heta displayed over ‘Elevation and Bathymetry’ background is given in Fig. 19. In addition, users can also choose whether or not to show places names as well as grid lines displaying latitude and longitude. Note the ‘Track Details (pressure)’ legend on the right side of screen.

Fig. 19

An example of a track of TC Heta displayed over ‘Elevation and Bathymetry’ background. Note the track details (pressure) legend on the right side of screen

Cyclone Details

In the pop-up box, select ‘show details’. Cyclone tracking points will now appear along the selected cyclone track as shown in Fig. 19. These points are colour coded as shown in the ‘Reference layers’ tab to indicate the intensity of the cyclones (where available). Arrows along the track indicate the direction of TC movement. Hovering the mouse pointer over a point along the cyclone track will display the cyclone name, time and central mean sea level pressure of the cyclone at that point. The latitude and longitude of the mouse position is also shown beneath the lower left edge of the map underneath the map scale. Clicking on a point on the track will bring up the pop-up information box.

Downloading Information

Users can download detailed information about individual cyclones from the pop-up box described above. The information can be downloaded as a CSV (Comma Separated Value, will open in Microsoft Excel). A CSV file contains best track data across the lifetime of the cyclone. Name, time, position and estimated intensity (in terms of central mean sea level pressure and 10 min averages sustained wind) are indicated. If there is no intensity estimate at particular point, ‘no estimates’ will be displayed in the data. An example of a ‘CSV’ file is shown in Table 2.

Table 2 An example of a ‘CSV’ file download of best track data for TC Yuri