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A detailed spectrally resolved extraterrestrial solar spectrum (ESS) is important for line‐by‐line radiative transfer modeling in the near‐IR. Very few observationally based high‐resolution ESS are available in this spectral region. Consequently, the theoretically calculated ESS by Kurucz has been widely adopted. We present the CAVIAR (Continuum Absorption at Visible and Infrared Wavelengths and its Atmospheric Relevance) ESS, which is derived using the Langley technique applied to calibrated observations using a ground‐based high‐resolution Fourier transform spectrometer (FTS) in atmospheric windows from 2000 to 10,000 cm–1 (1–5 µm). There is good agreement between the strengths and positions of solar lines between the CAVIAR and the satellite‐based Atmospheric Chemistry Experiment‐FTS ESS, in the spectral region where they overlap, and good agreement with other ground‐based FTS measurements in two near‐IR windows. However, there are significant differences in the structure between the CAVIAR ESS and spectra from semiempirical models. In addition, we found a difference of up to 8% in the absolute (and hence the wavelength‐integrated) irradiance between the CAVIAR ESS and that of Thuillier et al., which was based on measurements from the Atmospheric Laboratory for Applications and Science satellite and other sources. In many spectral regions, this difference is significant, because the coverage factor k = 2 (or 95% confidence limit) uncertainties in the two sets of observations do not overlap. Because the total solar irradiance is relatively well constrained, if the CAVIAR ESS is correct, then this would indicate an integrated “loss” of solar irradiance of about 30 W m–2 in the near‐IR that would have to be compensated by an increase at other wavelengths.

The study presents observed changes in climate extremes using daily precipitation and temperature data over 24 stations, covering the three climatic zones (Guinea coast, Savannah and Sahel) of Nigeria for the period 1971–2013. The data were homogenized with Expert Team on Climate Change Detection Indices (ETCCDI) RHtests version 4 software. RClimDex version 1.0 software was used to calculate 17 of the ETCCDI recommended precipitation and temperature extreme indices. The spatio‐temporal variation in the observed trends was analysed over each of the climatic zone. Results show a significant increase in the frequencies of warm spell, warm days and nights and decreasing cold spell, cold days and nights over the three climatic zones. A significant increase in annual total precipitation was found in some stations across the Guinea coast and Sahel zones. Changes in consecutive dry days and consecutive wet days are non‐significant in most stations. Also, a significant increase in extremely wet days was observed in a few stations across the three climatic zones. The implication of the observed warming could, however, result in thermal discomfort of lives in areas with significant positive trends. This could also exert pressure on the economy's power sector, as energy demand for cooling will increase. The increase in total annual precipitation will potentially be favourable for hydropower generation and increase the availability of the potable water supply for both industrial and domestic uses in the country. However, the increase in consecutive dry days and the decrease in consecutive wet days are dangerous for agricultural practices and, hence, food security.

Abstract:The extraterrestrial solar spectrum (ESS) is an important component in near infrared (near-IR) radiative transfer calculations. However, the impact of a particular choice of the ESS in these regions has been given very little attention. A line-by-line (LBL) transfer model has been used to calculate the absorbed solar irradiance and solar heating rates in the near-IR from 2000-10000 cm -1 (1-5 µm) using different ESS. For overhead sun conditions in a mid-latitude summer atmosphere, the absorbed irradiances could differ by up to about 11 Wm −2 (8.2 %) while the tropospheric and stratospheric heating rates could differ by up to about 0.13 K day −1 (8.1 %) and 0.19 K day −1 (7.6 %). The spectral shape of the ESS also has a small but non-negligible impact on these factors in the near-IR.

Abstract. Water vapour continuum absorption is potentially important for both closure of the Earth's energy budget and remote sensing applications. Currently, there are significant uncertainties in its characteristics in the near-infrared atmospheric windows at 2.1 and 1.6 µm. There have been several attempts to measure the continuum in the laboratory; not only are there significant differences amongst these measurements, but there are also difficulties in extrapolating the laboratory data taken at room temperature and above to temperatures more widely relevant to the atmosphere. Validation is therefore required using field observations of the real atmosphere. There are currently no published observations in atmospheric conditions with enough water vapour to detect a continuum signal within these windows or where the self-continuum component is significant. We present observations of the near-infrared water vapour continuum from Camborne, UK, at sea level using a Sun-pointing, radiometrically calibrated Fourier transform spectrometer in the window regions between 2000 and 10 000 cm−1. Analysis of these data is challenging, particularly because of the need to remove aerosol extinction and the large uncertainties associated with such field measurements. Nevertheless, we present data that are consistent with recent laboratory datasets in the 4 and 2.1 µm windows (when extrapolated to atmospheric temperatures). These results indicate that the most recent revision (3.2) of the MT_CKD foreign continuum, versions of which are widely used in atmospheric radiation models, requires strengthening by a factor of ∼5 in the centre of the 2.1 µm window. In the higher-wavenumber window at 1.6 µm, our estimated self- and foreign-continua are significantly stronger than MT_CKD. The possible contribution of the self- and foreign-continua to our derived total continuum optical depth is estimated by using laboratory or MT_CKD values of one, to estimate the other. The obtained self-continuum shows some consistency with temperature-extrapolated laboratory data in the centres of the 4 and 2.1 µm windows. The 1.6 µm region is more sensitive to atmospheric aerosol and continuum retrievals and therefore more uncertain than the more robust results at 2.1 and 4 µm. We highlight the difficulties in observing the atmospheric continuum and make the case for additional measurements in both the laboratory and field and discuss the requirements for any future field campaign.