Linden Ashcroft

Cold events over southern Australia: synoptic climatology and hemispheric structure.

Abstract Cold events (CEs) are an important feature of southern Australian weather. Unseasonably cold conditions can have a significant impact on Australia’s agricultural industry and other aspects of society. In this study the bottom 0.4% of maximum temperatures in Melbourne and Perth from the 1958–2006 period are defined as CEs, representing the large-scale patterns affecting most of extratropical Australia. Compiling 6-hourly progressions of the tracks of the cyclones and anticyclones that are geostrophically associated with CEs gives for the first time a detailed synoptic climatology over the area. The anticyclone tracks display a “cloud” of high density across the Indian Ocean, which is linked, in the mean, to weak but significant negative SST anomalies in the region. The cyclone tracks display much variability, with system origins ranging from subpolar to tropical. Several CEs are found to involve tropical and extratropical interaction or extratropical transition of originally tropical cyclones (hur...

Toward an integrated set of surface meteorological observations for climate science and applications

AbstractObservations are the foundation for understanding the climate system. Yet, currently available land meteorological data are highly fractured into various global, regional, and national holdings for different variables and time scales, from a variety of sources, and in a mixture of formats. Added to this, many data are still inaccessible for analysis and usage. To meet modern scientific and societal demands as well as emerging needs such as the provision of climate services, it is essential that we improve the management and curation of available land-based meteorological holdings. We need a comprehensive global set of data holdings, of known provenance, that is truly integrated both across essential climate variables (ECVs) and across time scales to meet the broad range of stakeholder needs. These holdings must be easily discoverable, made available in accessible formats, and backed up by multitiered user support. The present paper provides a high-level overview, based upon broad community input, ...

Drought variability and change across the Iberian Peninsula

Drought variability and change was assessed across the Iberian Peninsula over more than 100xa0years expanding through the twentieth century and the first decade of the twenty-first century. Daily temperature and precipitation data from 24 Iberian time series were quality controlled and homogenized to create the Monthly Iberian Temperature and Precipitation Series (MITPS) for the period 1906–2010. The Standardized Precipitation Index (SPI), driven only by precipitation, and the Standardized Precipitation Evapotranspiration Index (SPEI), based on the difference between the precipitation and the reference evapotranspiration (ET0), were computed at annual and seasonal scale to describe the evolution of droughts across time. The results confirmed that a clear temperature increase has occurred over the entire Iberian Peninsula at the annual and seasonal scale, but no significant changes in precipitation accumulated amounts were found. Similar drought variability was provided by the SPI and SPEI, although the SPEI showed greater drought severity and larger surface area affected by drought than SPI from 1980s to 2010 due to the increase in atmospheric evaporative demand caused by increased temperatures. Moreover, a clear drying trend was found by the SPEI for most of the Iberian Peninsula at annual scale and also for spring and summer, although the SPI did not experience significant changes in drought conditions. From the drying trend identified for most of the Iberian Peninsula along the twentieth century, an increase in drought conditions can also be expected for this region in the twenty-first century according to future climate change projections and scenarios.

Recent Developments in Australian Climate History

There have been considerable advances in historical climatology in Australia over the past decade. Recent interdisciplinary research using documentary and early instrumental records has identified twenty-four new drought events and seventeen major wet periods for eastern New South Wales over the 1788–1899 period. These results provide the first opportunity to use well-verified historical Australian rainfall data in long-term global drought studies. While considerable progress has been made using material collected from the main population centres of New South Wales, Victoria, Tasmania, South Australia, and Queensland, there is still great potential to recover more colonial-era data from many parts of the country.

Current climate data rescue activities in Australia

Recovering historical instrumental climate data is crucial for identifying long-term climate variability and change, putting present climate into context and constraining future climate projections (Brunet and Jones, 2011). In other words, to understand the future, we need to improve our understanding of the past. n nClimate data rescue is a well-established practice in many Northern Hemisphere countries, where the instrumental record can stretch back several centuries [e.g., Parker et al. (1992) for England, and Slonosky (2002) for France]. In Australia, however, the recovery and analysis of historical weather observations has not been the subject of such dedication until recently.