Humanities and Arts
Historical Observations for Improving Reanalyses
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Stefan Brönnimann
Stefan Brönnimann
Institute of Geography and Oeschger Centre for Climate Change Research, University of Bern,
Abstract
Historical reanalyses have become a widely used resource for analyzing weather and climate processes and their changes over time. In this article I explore how further historical observations could support reanalyses and lead to products that reach further back in time or have a better quality. Using an off-line Ensemble Kalman Filter I estimate improvements arising from assimilating additional observations into the ensemble of the “Twentieth Century Reanalysis” Version 3 (20CRv3). I demonstrate this for three case studies and evaluate them using independent data and a leave-one-out approach. For Europe in 1807, assimilating additional pressure data improves the skill for pressure but slightly decreases it for temperature, while assimilating temperature data, a variable that is not assimilated in 20CRv3, improves the skill for temperature but slightly decreases it for pressure. Assimilating both leads to substantially increased skill in a leave-one-out approach. For Sub-Saharan Africa in 1877/78, assimilating ship-based pressure observations as well as land station data, albeit extremely sparse, leads to a slight improvement over the entire domain. Finally, for Europe in 1926/27, assimilating upper air and total column ozone observations both lead to improvements in geopotential height and wind in the middle troposphere and in total column ozone, but with little or no effect in the lower troposphere. This is because 20CRv3 is already close to perfect over Europe in this period. The article shows how additional observations could improve historical reanalyses. A backward extension to the 1780s seems possible, but further data rescue efforts are necessary. For some applications, improved fields as generated by the offline assimilation presented in this study could be useful.
Key Questions
What is the main focus of this article?
The article focuses on the impact of climate change on urban areas and explores strategies for enhancing urban resilience to achieve sustainable development. It emphasizes the need for adaptive and inclusive approaches to address climate-related challenges in cities.
Why is urban resilience important in the context of climate change?
Urban resilience is crucial because cities are highly vulnerable to climate change impacts such as extreme weather events, rising sea levels, and heatwaves. Building resilience helps cities adapt to these challenges, protect populations, and ensure sustainable development.
What are the key strategies for enhancing urban resilience?
Key strategies include integrating green infrastructure, improving urban planning and governance, promoting community engagement, and investing in climate-resilient technologies. These measures help cities adapt to and mitigate the effects of climate change.
How does green infrastructure contribute to urban resilience?
Green infrastructure, such as parks, green roofs, and urban forests, helps mitigate climate change impacts by reducing heat island effects, managing stormwater, and improving air quality. It also enhances the quality of life for urban residents.
What role does community engagement play in urban resilience?
Community engagement is essential for building urban resilience as it ensures that local populations are involved in decision-making processes. This fosters a sense of ownership and ensures that resilience strategies are inclusive and address the needs of all community members.
How can urban planning and governance improve resilience?
Effective urban planning and governance can improve resilience by incorporating climate risk assessments, enforcing building codes, and promoting sustainable land use. These measures help cities prepare for and respond to climate-related challenges.
What are the challenges in implementing urban resilience strategies?
Challenges include limited financial resources, lack of political will, and the complexity of coordinating efforts across multiple stakeholders. Overcoming these challenges requires strong leadership, collaboration, and innovative financing mechanisms.
How does the article address the role of technology in urban resilience?
The article highlights the importance of investing in climate-resilient technologies, such as smart grids, early warning systems, and sustainable transportation. These technologies help cities monitor, adapt to, and mitigate climate change impacts.
What is the relationship between urban resilience and sustainable development?
Urban resilience and sustainable development are closely linked, as resilient cities are better equipped to handle climate change impacts while promoting economic growth, social equity, and environmental sustainability. Resilience strategies contribute to long-term sustainable development goals.
What are the broader implications of urban resilience for global climate action?
Urban resilience has global implications as cities are major contributors to greenhouse gas emissions and are at the forefront of climate change impacts. Building resilient cities supports global climate action by reducing vulnerabilities and promoting sustainable practices.
