Volcanic effects on climate: revisiting the mechanisms
نویسندگان
چکیده
The characteristics of planetary wave energy propagation are being compared based on NCEP reanalysis data from 1958 to 2002 between boreal winters after strong volcanic eruptions, non-volcanic winters and episodes of strong polar vortex lasting at least 30 days. It shows that in the volcanically disturbed winters much more planetary wave energy is produced in the troposphere, passes through the lowermost stratosphere and enters the upper stratosphere than in any other times. This is contradicting earlier interpretations and model simulations. Possibly the observed El Ninos coinciding with the three significant eruptions in the second half of the 20th century contributed to the planetary wave energy. In order to produce the observed robust climate anomaly patterns in the lower troposphere, these planetary waves are suggested to be reflected near the stratopause instead of breaking. While a strong polar vortex is observed after volcanic eruptions in the stratosphere and in the troposphere, specific episodes of strong polar vortex regime exhibit much stronger anomalies and different dynamics. Hence it is suggested that the climate effects of volcanic eruptions are not being explained by the excitation of inherent zonal mean variability modes such as Strong Polar Vortex or Northern Annular Mode, but rather is another mode that possibly reflects upon the North Atlantic Oscillation.
منابع مشابه
Interactive comment on “ Volcanic effects on climate : revisiting the mechanisms ” by H . - F . Graf
The paper addresses an important problem of mechanisms of sensitivity of highlatitude circulation with respect to volcanic forcing. The authors attempted to distinguish two major mechanisms based on reflection and refraction of planetary waves using analysis of NCEP data assimilation output for the period from 1958 to 2002. All previous data analyses were conducted using mostly surface data. Th...
متن کاملVolcanic Eruptions and Climate
Volcanic eruptions are an important natural cause of climate change on many timescales. A new capability to predict the climatic response to a large tropical eruption for the succeeding 2 years will prove valuable to society. In addition, to detect and attribute anthropogenic influences on climate, including effects of greenhouse gases, aerosols, and ozone-depleting chemicals, it is crucial to ...
متن کاملPersistent drying in the tropics linked to natural forcing.
Approximately half of the world's population lives in the tropics, and future changes in the hydrological cycle will impact not just the freshwater supplies but also energy production in areas dependent upon hydroelectric power. It is vital that we understand the mechanisms/processes that affect tropical precipitation and the eventual surface hydrological response to better assess projected fut...
متن کاملVolcanic forcing of climate over the past 1500 years: An improved ice core-based index for climate models
[1] Understanding natural causes of climate change is vital to evaluate the relative impacts of human pollution and land surface modification on climate. We have investigated one of the most important natural causes of climate change, volcanic eruptions, by using 54 ice core records from both the Arctic and Antarctica. Our recently collected suite of ice core data, more than double the number o...
متن کامل