Mauna Loa Observatory Research Articles

Atmospheric opacity using 220 GHz (1.36 mm) radiometer data and water vapor trends over Indian Astronomical Observatory (IAO), Hanle

The present work reports atmospheric opacity at 220 GHz over Indian Astronomical Observatory (IAO)-Hanle during 2006 to 2018. The opacity data were derived from the radiometric measurement of sky-brightness temperature as a function of zenith angle for every 10 min during day and night. Since the operating frequency range is not completely opaque during rainfall or cloudy atmosphere, observations are performed even during rainfall or cloudy sky conditions. The minimum opacities observed at the site varied from 0.06-0.07 at 1st quartile and 0.08-0.09 at 2nd quartile during December-January. Opacity at Hanle is linearly correlated with high temporal resolution GPS (Global Positioning System) Precipitable Water Vapor (PWV) with a correlation coefficient of about 0.8. The observed median opacity at Hanle has increased by 44% during the best observing months (October–March) and 24% over the annual data (October-September) with reference to the opacity observed during 2000–2003. Such increasing opacity trends are apparently due to effects of the dynamics of the regional and global hydrological cycle. In order to assess the impacts of the regional and global hydrological cycle, PWV obtained from AErosol RObotic NETwork (AERONET), satellite and reanalysis data were studied at nine high-altitude astronomical observatories spread spatially across the globe such as Atacama desert in Chile, Mauna Loa Observatory in Hawaii, Hanle and Merak in India, Ali and Yangbajing Observatories in Tibet, LLAMA in Argentina, and Dome A and Dome C in the Antarctic Plateau during 2003-2018. On an average, PWV trend over Atacama desert is increasing by 0.01 to 0.03 mm per year and at IAO-Hanle, Merak and Ali by 0.01 to 0.05 mm per year, indicating non uniform dynamic hydrological cycles. Interestingly, there is no noticeable PWV trend for the sites located in the Antarctic Plateau. During the four best observing months, PWV observed at Hanle, Merak and Ali sites have values lower than the Mauna Loa observatory by 0.14 mm and 0.56 mm at 1st and 2nd quartiles, respectively.

Optical Modeling of Single Asian Dust and Marine Air Particles: A Comparison with Geometric Particle Shapes for Remote Sensing

We compare the optical properties of various geometric shapes with single atmospheric Asian dust and marine background air particles collected at Mauna Loa Observatory. Three-dimensional representations of the particles were acquired with focused ion-beam (FIB) tomography, which involves FIB milling of individual particles followed by imaging and elemental mapping with scanning electron microscopy. Particles were heterogeneous with mainly dolomite or calcite and a minor amount of iron; marine air particles contained gypsum but no iron. Extinction and backscatter fraction were calculated with the discrete dipole approximation method. Geometric shapes were grouped as ellipsoids (sphere, spheroid, ellipsoid), cuboids (cube, square prism, rectangular prism), and pyramids (tetrahedron, triangular pyramid). Each group represented a progression of shapes with 1, 2, or 3 non-identical axes. Most shapes underestimated particle extinction and overestimated the backscatter fraction. Not surprisingly, extinction and the backscatter fraction of the sphere and cube were furthest from those of the particles. While the 3-axis ellipsoid and rectangular prism were closer dimensionally to the particles, extinction and the backscatter fraction for the 2-axis spheroid and square prism, respectively, were often closer to the particles. The extinction and backscatter fraction for the tetrahedron and triangular pyramid were closer on average to the actual particles than were the other shapes. Tetrahedra have the advantage that parameterization of an aerosol model for remote sensing would not require an aspect ratio distribution. Particle surface roughness invariably decreased the backscatter fraction. While surface roughness typically contributes a minor part to overall scattering, in some cases the larger surface area of the tetrahedron and triangular pyramid sufficiently accounted for enhanced forward scattering of particles from surface roughness.

ENSO and Southeast Asian biomass burning modulate subtropical trans-Pacific ozone transport.

Trans-Pacific transport of enhanced ozone plumes has been mainly attributed to fossil fuel combustion in Asia in spring, but less attention has been paid to vegetation fires in Asia. Here we show that the El Niño-Southern Oscillation (ENSO)-modulated fires in Southeast Asia, rather than Asian fossil fuel plumes, dominate the interannual variability of springtime trans-Pacific transport of ozone across the entire North Pacific Ocean. During El Niño springs, the intensified fires from both the Indochinese Peninsula and Indonesia, together with large-scale circulation anomalies, result in enhanced ozone plumes that stretch over 15 000 km in both the lower-middle and upper troposphere. This enhancement is also observed in the in situ measurements of ozone concentration, with an almost 10% increase at Mauna Loa Observatory, Hawaii, a unique site to monitor the long-distance transport over the North Pacific. This study reports an unexpectedly strong influence of vegetation fires, linked with climate variability, on global tropospheric chemistry and proves once more how complex the interactions in the climate system are.

Use of Multiple Lines of Evidence to Understand Reactive Mercury Concentrations and Chemistry in Hawai'i, Nevada, Maryland, and Utah, USA.

To advance our understanding of the mercury (Hg) biogeochemical cycle, concentrations and chemistry of gaseous oxidized Hg (GOM), particulate-bound Hg (PBM), and reactive Hg (RM = GOM + PBM) need to be known. The UNR-RMAS 2.0 provides a solution that will advance knowledge. From 11/2017 to 02/2019, the RMAS 2.0 was deployed in Hawai'i, Nevada, Maryland, and Utah to test system performance and develop an understanding of RM at locations impacted by different atmospheric oxidants. Mauna Loa Observatory, Hawai'i, impacted by the free troposphere and the marine boundary layer, had primarily -Br/Cl RM compounds. The Nevada location, directly adjacent to a major interstate highway and experiences inputs from the free troposphere, exhibited -Br/Cl, -N, -S, and organic compounds. In Maryland, compounds observed were -N, -S, and organic-Hg. This site is downwind of coal-fired power plants and located in a forested area. The location in Utah is in a basin impacted by oil and natural gas extraction, multiday wintertime inversion episodes, and inputs from the free troposphere. Compounds were -Br/Cl or -O, -N, and -Br/Cl. The chemical forms of RM identified were consistent with the air source areas, predominant ion chemistry, criterion air pollutants, and meteorology.

Development of on-site self-calibration and retrieval methods for sky-radiometer observations of precipitable water vapor

Abstract. The Prede sky radiometer measures direct solar irradiance and the angular distribution of diffuse radiances at the ultraviolet, visible, and near-infrared wavelengths. These data are utilized for the remote sensing of aerosols, water vapor, ozone, and clouds, but the calibration constant, which is the sensor output current of the extraterrestrial solar irradiance at the mean distance between Earth and the Sun, is needed. The aerosol channels, which are the weak gas absorption wavelengths of 340, 380, 400, 500, 675, 870, and 1020 nm, can be calibrated by an on-site self-calibration method, the Improved Langley method. This on-site self-calibration method is useful for the continuous long-term observation of aerosol properties. However, the continuous long-term observation of precipitable water vapor (PWV) by the sky radiometer remains challenging because calibrating the water vapor absorption channel of 940 nm generally relies on the standard Langley (SL) method at limited observation sites (e.g., the Mauna Loa Observatory) and the transfer of the calibration constant by a side-by-side comparison with the reference sky radiometer calibrated by the SL method. In this study, we developed the SKYMAP algorithm, a new on-site method of self-calibrating the water vapor channel of the sky radiometer using diffuse radiances normalized by direct solar irradiance (normalized radiances). Because the sky radiometer measures direct solar irradiance and diffuse radiance using the same sensor, the normalization cancels the calibration constant included in the measurements. The SKYMAP algorithm consists of three steps. First, aerosol optical and microphysical properties are retrieved using direct solar irradiances and normalized radiances at aerosol channels. The aerosol optical properties at the water vapor channel are interpolated from those at aerosol channels. Second, PWV is retrieved using the angular distribution of the normalized radiances at the water vapor channel. Third, the calibration constant at the water vapor channel is estimated from the transmittance of PWV and aerosol optical properties. Intensive sensitivity tests of the SKYMAP algorithm using simulated data of the sky radiometer showed that the calibration constant is retrieved reasonably well for PWV<2 cm, which indicates that the SKYMAP algorithm can calibrate the water vapor channel on-site in dry conditions. Next, the SKYMAP algorithm was applied to actual measurements under the clear-sky and low-PWV (<2 cm) conditions at two sites, Tsukuba and Chiba, Japan, and the annual mean calibration constants at the two sites were determined. The SKYMAP-derived calibration constants were 10.1 % and 3.2 % lower, respectively, than those determined by a side-by-side comparison with the reference sky radiometer. After determining the calibration constant, we obtained PWV from the direct solar irradiances in both the dry and wet seasons. The retrieved PWV values corresponded well to those derived from a global-navigation-satellite-system–global-positioning-system receiver, a microwave radiometer, and an AERONET (Aerosol Robotic Network) sun–sky radiometer at both sites. The correlation coefficients were greater than 0.96. We calculated the bias errors and the root mean square errors by comparing PWV between the DSRAD (direct solar irradiance) algorithm and other instruments. The magnitude of the bias error and the root mean square error were <0.163 and <0.251 cm for PWV<3 cm, respectively. However, our method tended to underestimate PWV in the wet conditions, and the magnitude of the bias error and the root mean square error became large, <0.594 and <0.722 cm for PWV>3 cm, respectively. This problem was mainly due to the overestimation of the aerosol optical thickness before the retrieval of PWV. These results show that the SKYMAP algorithm enables us to observe PWV over the long term, based on its unique on-site self-calibration method.

Following Carbon Dioxide Concentration and Consequences of its Zero Emission on the Environmental Ecosystem

Background: This research aims to follow the concentration of carbon dioxide (CO2) in the atmosphere and the effect of zero-emission on the ecosystem. CO2 is the most important of the green house gases. Nowadays, the earth is suffering from global warming due to greenhouse gases. The call all over the world is to reduce the emission of the greenhouse gases, mainly CO2. Methods: The research methodology depends on the data of international research laboratories, which follow the concentration of CO2, such as National Oceanic and Atmospheric Administration (NOAA), the USA, and Mauna Loa Observatory in Hawaii. The concern towards CO2 concentration in the atmosphere started in the last century. Results: The industrial revolution did not consider the impact of pollution on the environment. The impact on the environment was noticed only after a clear disturbance in the ecosystem. The emission of greenhouse gases, especially, CO2 is monitored; daily, monthly and yearly. There are different sources of CO2 emissions, such as transportation, factories, burning of forests etc. In fact, CO2 is a harmful as well as a useful gas. It is harmful because of global warming, and useful because of its important role in the photosynthesis process. This process is very crucial for all living things. The research to reduce the emission of CO2. has provided some solutions. Layered materials, MPS3, where M stands for the transition metal, have been used to store hydrogen gas. The hydrogen molecule size is 2.89 Å, and the molecular size of CO2 is 3.3 Å, this means that the CO2 can be captured by the layered materials. The capturing of CO2 is achieved by simulation. Conclusion: We need to reduce the emission of CO2 but not to reach zero emission, because then, there will be no photosynthesis process, which means there will be no life on the earth. Carbon capture and storage is a technology that can capture up to 90% of the CO2, but the biggest obstacle to this approach lies in the inherent thermodynamic stability and kinetic inertness of CO2.

Long-term Variability of Aerosol Optical Properties at Mauna Loa

ABSTRACT We investigated the variability of the aerosol scattering (σsp; 1974–2015) and absorption (σap; 2000–2015) coefficients at the Mauna Loa Observatory using surface in situ measurements. Although σsp decreased during the morning (1.85 ± 3.43 Mm–1 at 550 nm, 8–11 local standard time [LST]), it increased during the afternoon (3.72 ± 7.63 Mm–1 at 550 nm, 14–17 LST) due to the development of thermally induced boundary layer winds. No distinct diurnal variation was observed in σap. The obvious increase in σsp and σap during the spring under free troposphere conditions (8–11 LST) is attributed to long-range-transported aerosols from Asia, especially dust and pollution aerosols from Northeast Asia and biomass burning aerosols from Southeast Asia. Accordingly, σsp increased from 1974 till 2015 (at 1.89% year–1), whereas no significant trend was noted for either σsp or σap from 2000 till 2015. An increasing trend for σsp prevailed in air masses originating in Northeast Asia (+0.51 Mm–1 decade–1).

Fungal aerobiota are not affected by time nor environment over a 13-y time series at the Mauna Loa Observatory

Fungi are ubiquitous and often abundant components of virtually all ecosystems on Earth, serving a diversity of functions. While there is clear evidence that fungal-mediated processes can influence environmental conditions, and in turn select for specific fungi, it is less clear how fungi respond to environmental fluxes over relatively long time frames. Here we set out to examine changes in airborne fungi collected over the course of 13 y, which is the longest sampling time to date. Air filter samples were collected from the Mauna Loa Observatory (MLO) on Hawaii Island, and analyzed using Illumina amplicon sequencing. As a study site, MLO is unique because of its geographic isolation and high elevation, making it an ideal place to capture global trends in climate and aerobiota. We found that the fungal aerobiota sampled at MLO had high species turnover, but compositional similarity did not decrease as a function of time between samples. We attribute these patterns to neutral processes such as idiosyncratic dispersal timing and trajectories. Furthermore, the composition of fungi at any given point was not significantly influenced by any local or global environmental variables we examined. This, and our additional finding of a core set of persistent fungi during our entire sampling period, indicates some degree of stability among fungi in the face of natural environmental fluctuations and human-associated global change. We conclude that the movement of fungi through the atmosphere is a relatively stochastic process.

Scaling Properties of Atmospheric Wind Speed in Mesoscale Range

The scaling properties of turbulent flows are well established in the inertial sub-range. However, those of the synoptic-scale motions are less known, also because of the difficult analysis of data presenting nonstationary and periodic features. Extensive analysis of experimental wind speed data, collected at the Mauna Loa Observatory of Hawaii, is performed using different methods. Empirical Mode Decomposition, interoccurrence times statistics, and arbitrary-order Hilbert spectral analysis allow to eliminate effects of large-scale modulations, and provide scaling properties of the field fluctuations (Hurst exponent, interoccurrence distribution, and intermittency correction). The obtained results suggest that the mesoscale wind dynamics owns features which are typical of the inertial sub-range turbulence, thus extending the validity of the turbulent cascade phenomenology to scales larger than observed before.

Temperature trends in Hawaiʻi: A century of change, 1917–2016

Based on a revised and extended multi‐station Hawaiʻi Temperature Index (HTI), the mean air temperature in the Hawaiian Islands has warmed significantly at 0.052°C/decade (p < 0.01) over the past 100 years (1917–2016). The year 2016 was the warmest year on record at 0.924°C above the 100‐year mean (0.202°C). During each of the last four decades, mean state‐wide positive air temperature anomalies were greater than those of any of the previous decades. Significant warming trends for the last 100 years are evident at low‐ (0.056°C/decade, p < 0.001) and high‐elevations (0.047°C/decade, p < 0.01). Warming in Hawai‘i is largely attributed to significant increases in minimum temperature (0.072°C/decade, p < 0.001) resulting in a corresponding downward trend in diurnal temperature range (−0.055°C/decade, p < 0.001) over the 100‐year period. Significant positive correlations were found between HTI, the Pacific Decadal Oscillation, and the Multivariate ENSO Index, indicating that natural climate variability has a significant impact on temperature in Hawaiʻi. Analysis of surface air temperatures from NCEP/NCAR reanalysis data for the region of Hawaiʻi over the last 69 years (1948–2016) and a mean atmospheric layer temperature time series calculated from radiosonde‐measured thickness (distance between constant pressure surfaces) data over the last 40 years (1977–2016) give results consistent with the HTI. Finally, we compare temperature trends for Hawaii's highest elevation station, Mauna Loa Observatory (3,397 m), to those on another mountainous subtropical island station in the Atlantic, Mt. Izaña Observatory (2,373 m), Tenerife, Canary Islands. Both stations sit above the local temperature inversion layer and have virtually identical significant warming trends of 0.19°C/decade (p < 0.001) between 1955 and 2016.

Analysis and Optical Modeling of Individual Heterogeneous Asian Dust Particles Collected at Mauna Loa Observatory.

We have determined optical properties of heterogeneous particles from aerosol samples collected at Hawaii's Mauna Loa Observatory. Back trajectories, satellite imagery, and composition differences among particles from scanning electron microscopy revealed a subset of particles with dolomite or calcite that likely came from Asia. Using focused ion-beam tomography and the discrete dipole approximation, we show how small amounts of an iron phase (oxide or carbonate), or in one case soot, affected extinction and scattering compared with particles of neat dolomite or calcite. We show how particles exhibit a range scattering values due to varying orientations of the inclusion phases. Extinction efficiencies for the heterogeneous particles with dolomite (3.47) and calcite (3.36) were 19% to 21% lower than extinction for marine background air particles (3.72). Extinction for the Asian dust was, however, generally higher than for the neat particles. Compared to iron carbonate, the presence of an absorbing iron oxide affected scattering in Asian dust particles even at the low oxide concentrations studied here (0.6% to 8.1%). Scattering efficiency decreased by <1% with a 1% increase in hematite but by 2% to 5% with magnetite. Asian dust scattered light strongly forward, but backscattering was 56% larger than for the marine background air particles. Backscattering in the Asian dust was also larger with magnetite than hematite. Single scattering albedo for Asian dust with hematite, magnetite, or soot averaged 0.96 ± 0.06 but was as low as 0.72 with a magnetite mass of 5.8%.

Measuring and Visualizing Solar UV for a Wide Range of Atmospheric Conditions on Hawai'i Island.

Hawai’i Island often receives extreme (UV Index ≥ 11) solar ultraviolet radiation (UVR). While the UV Index (UVI) has been measured since 1997 at Hawai’i’s high-altitude Mauna Loa Observatory (MLO), measurements where people live and recreate are rare. We measured UVI on the face of a rotating mannequin head with UVR sensors at its eyes, ears and cheeks while simultaneously measuring the UVI with a zenith-facing sensor at MLO and seven sites at or near sea level from 19 July to 14 August 2018. The mannequin sensors received higher UVR at midmorning and midafternoon than at noon. For example, at sea level the peak UVI at the left cheek was 5.2 at midmorning and 2.9 at noon, while the horizontal UVI at noon was 12.7. Our measurements were supplemented with wide-angle (190° and 360°) sky photographs and UV images of the mannequin head. Because the UVI applies to horizontal surfaces, people in tropical and temperate latitudes should be informed that their face may be more vulnerable to UVR at midmorning and midafternoon than at noon. Finally, our instruments provided opportunities to measure unexpected UVR-altering events, including rare biomass smoke over MLO and spectroscopic measurements of substantial UVR-absorbing sulfur dioxide in the eruption plume of the Kilauea volcano.

A calibration procedure which accounts for non-linearity in single-monochromator Brewer ozone spectrophotometer measurements

Abstract. It is now known that single-monochromator Brewer spectrophotometer ozone and sulfur dioxide measurements suffer from non-linearity at large ozone slant column amounts due to the presence of instrumental stray light caused by scattering within the optics of the instrument. Because of the large gradient in the ozone absorption spectrum in the near-ultraviolet, the atmospheric spectra measured by the instrument possess a very large gradient in intensity in the 300 to 325 nm wavelength region. This results in a significant sensitivity to stray light when there is more than 1000 Dobson units (DU) of ozone in the light path. As the light path (air mass) through ozone increases, the stray-light effect on the measurements also increases. The measurements can be of the order of 10 %, low for an ozone column of 600 DU and an air mass factor of 3 (1800 DU slant column amount), which is an example of conditions that produce large slant column amounts. Primary calibrations for the Brewer instrument are carried out at Mauna Loa Observatory in Hawaii and Izana Observatory in Tenerife. They are done using the Langley plot method to extrapolate a set of measurements made under a constant ozone vertical column to an extraterrestrial calibration constant. Since the effects of a small non-linearity at moderate ozone paths may still be important, a better calibration procedure should account for the non-linearity of the instrument response. Studies involving the scanning of a laser source have been used to characterize the stray-light response of the Brewer (Fioletov et al., 2000), but until recently these data have not been used to elucidate the relationship between the stray-light response and the ozone measurement non-linearity. In a study done by Karppinen et al. (2015), a method for correcting stray light has been presented that uses an additive correction, which is determined via instrument slit characterization and a radiative transfer model simulation and is then applied to the single Brewer data (Karppinen et al., 2015). The European Brewer Network is also applying stray-light corrections, which includes an iterative process that results in correcting the single Brewer data to agree with double Brewer data (Rimmer et al., 2018; Redondas et al., 2018). The first model requires measurements of the slit function and the latter method relies on a calibrated instrument, such as a double Brewer, to characterize the instrument and to determine a correction for stray light. This paper presents a simple and practical method to correct for the effects of stray light, which includes a mathematical model of the instrument response and a non-linear retrieval approach that calculates the best values for the model parameters. The model can then be used in reverse to provide more accurate ozone values up to a defined maximum ozone slant path. The parameterization used was validated using an instrument physical model simulation. This model can be applied independently to any Brewer instrument and correct for the effects of stray light.

Editorial: Long‐term studies in limnology and oceanography

We use a variety of approaches and techniques to study aquatic ecosystems. Among the most powerful of these are studies that involve repeated measurements of the same variables over longer periods (i.e., many years to decades). The reason for this is that changes in our streams, rivers, lakes, wetlands, estuaries, and oceans may take place and are only observable over prolonged periods. Consequently, we need systematic and sustained environmental monitoring to document the effects of global change on aquatic ecosystems and understand its causes and consequences. The case that long-term research is instrumental in advancing scientific knowledge and policy was made in two recent publications entitled, “Long-term studies contribute disproportionately to ecology and policy” (Hughes et al. 2017. Bioscience) and “Long-term research in ecology and evolution: a survey of challenges and opportunities” (Kuebbing et al. 2018. Ecological Monographs). These papers found that long-term studies are cited more, are more likely to be published in highly regarded scientific journals, and play a larger role in shaping environmental policy. Despite this, long-term studies constitute a small fraction of aquatic science research. From my quick survey, only 5–6% of publications on lakes, oceans, estuaries, and rivers include long-term data collections (data from Clarivate Analytics Web of Science for papers published between 1981 and 2018). Is long-term monitoring vital for aquatic sciences and should we be doing more of these studies? I think so. There are many examples where continuous time-series documented ecosystem change and allowed for stakeholders and decision makers to work together to reduce or fix the problem. Acid rain provides perhaps one of the most famous examples of the value of long-term research. A series of measurements in northeast U.S.A., eastern Canada, and Europe demonstrated declining pH in rain, snow, and water that resulted in measurable impacts on lake ecosystems. Another example of the value of long-term data collection are the continuing observations of atmospheric levels of carbon dioxide (CO2) at the Mauna Loa Observatory in Hawaii which eventually provided clues about the changing global climate. Coupled to the atmospheric CO2 records are 30 years of rising seawater partial pressure CO2 measurements at nearby station ALOHA, which have been accompanied by simultaneous increases in ocean acidity. It can take many years to see the benefits of long-term data collection. Unfortunately, long-term studies are chronically underfunded in many countries and can be difficult to sustain through multiple grant cycles. Granting agencies generally promote research that provides immediate tangible products and benefits and typically fund studies for limited durations (1–5 years). Compounding this funding problem is the issue that many of us do a poor job of explaining the necessity and importance of long-term research to the public. Even among our peers, the value of long-term research can be a tough sell. I recently asked two of my Canadian colleagues to review one of my grant applications, which included the prospect of long-term research. Although one of my colleagues encouraged me to increase the long-term monitoring facet of my proposal, the other one was more critical. It was suggested to me to de-emphasize this aspect of my proposal because of the perception that the review panel would not consider it novel and would hesitate to allocate public research dollars to long-term monitoring research. Altogether, we must do better to promote long-term studies and the many benefits that they provide. Not only can a long-term time-series generate unique knowledge, but it can also lead to the discovery of surprise findings. We should support our peers through their long-term research endeavors and remind our politicians and funding agencies that long-term studies are essential to the creation of effective environmental policy. This past year, we at Limnology and Oceanography celebrated the anniversaries of two long-term monitoring research sites with the creation of two virtual issues; the 30th Anniversary of the Hawaii Ocean Time-series (https://aslopubs.onlinelibrary.wiley.com/doi/toc/10.1002/(ISSN)1939-5590.ALOHA30) and the 50th Anniversary of the Experimental Lakes Area (https://aslopubs.onlinelibrary.wiley.com/doi/toc/10.1002/(ISSN)1939-5590.ELA50?campaign=dartwol|4795815320). We are finishing the year with this capstone special issue on long-term perspectives in aquatic research. But let us not end there. I hope to see more long-term studies published in Limnology and Oceanography.

The global temperature anomalies related to the slowdown of atmospheric CO2 concentration observed from 1939 up to 1950

It is very well known that carbon dioxide (CO2) accumulated in the atmosphere is the main climate driver. The first precise direct continuous measurements of the atmospheric CO2concentration were provided from Keeling since 1958 at Mauna Loa Observatory. The measurements are going on up to day. Law Dom ice core drilling was started in 1969 by the Australian ANARE program. The slowdown of the World economic development during the World War I, the Great Depression and the World War II, lead to deaccelerating the CO2 emissions. The integration of the total CO2emissions using the impulse response function concept shows that the observed slowdown of the CO2 emission is not sufficient to explain the CO2 plateau and additional CO2 sinks are necessary. Based on multiple regression models adjusted global temperatures were determined by removal of temperature influences other than related to CO2. The adjusted temperatures follow close the CO2 radiation term. The difference between the estimated adjusted temperature time evolution with and without the CO2 slowdown and also the short time trends demonstrate very clear the close relation between the temperature change and the CO2 radiative forcing. It is shown that the slowdown of the CO2 emission in the period from 1939 up to 1950 and the related CO2 concentration in the atmosphere, caused at least partially by human activities, generate a more slow increase of the temperature anomalies. Consequently CO2 is the leading variable of the relation surface temperature - CO2.

Metrology of solar spectral irradiance at the top of the atmosphere in the near infrared measured at Mauna Loa Observatory: the PYR-ILIOS campaign

Abstract. The near-infrared (NIR) part of the solar spectrum is of prime importance for solar physics and climatology, directly intervening in the Earth's radiation budget. Despite its major role, available solar spectral irradiance (SSI) NIR datasets, space-borne or ground-based, present discrepancies caused by instrumental or methodological reasons. We present new results obtained from the PYR-ILIOS SSI NIR ground-based campaign, which is a replication of the previous IRSPERAD campaign which took place in 2011 at the Izaña Atmospheric Observatory (IZO). We used the same instrument and primary calibration source of spectral irradiance. A new site was chosen for PYR-ILIOS: the Mauna Loa Observatory (MLO) in Hawaii (3397 m a.s.l.), approximately 1000 m higher than IZO. Relatively to IRSPERAD, the methodology of monitoring the traceability to the primary calibration source was improved. The results as well as a detailed error budget are presented. We demonstrate that the most recent results, from PYR-ILIOS and other space-borne and ground-based experiments, show an NIR SSI lower than the previous reference spectrum, ATLAS3, for wavelengths above 1.6 µm.

The instrument constant of sky radiometers (POM-02) – Part 1: Calibration constant

Abstract. Ground-based networks have been developed to determine the spatiotemporal distribution of the optical properties of aerosols using radiometers. In this study, the precision of the calibration constant (V0) for the sky radiometer (POM-02) that is used by SKYNET was investigated. The temperature dependence of the sensor output was also investigated, and the dependence in the 340, 380, and 2200 nm channels was found to be larger than for other channels and varied with the instrument. In the summer, the sensor output had to be corrected by a factor of 1.5 % to 2 % in the 340 and 380 nm channels and by 4 % in the 2200 nm channel in the measurements at Tsukuba (36.05∘ N, 140.13∘ E), with a monthly mean temperature range of 2.7 to 25.5 ∘C. In the other channels, the correction factors were less than 0.5 %. The coefficient of variation (CV, standard deviation/mean) of V0 from the normal Langley method, based on the data measured at the NOAA Mauna Loa Observatory, is between 0.2 % and 1.3 %, except in the 940 nm channel. The effect of gas absorption was less than 1 % in the 1225, 1627, and 2200 nm channels. The degradation of V0 for wavelengths shorter than 400 nm (−10 % to −4 % per year) was larger than that for wavelengths longer than 500 nm (−1 to nearly 0 % per year). The CV of V0 transferred from the reference POM-02 was 0.1 % to 0.5 %. Here, the data were simultaneously taken at 1 min intervals on a fine day, and data when the air mass was less than 2.5 were compared. The V0 determined by the improved Langley (IML) method had a seasonal variation of 1 % to 3 %. The root mean square error (RMSE) from the IML method was about 0.6 % to 2.5 %, and in some cases the maximum difference reached 5 %. The trend in V0 after removing the seasonal variation was almost the same as for the normal Langley method. Furthermore, the calibration constants determined by the IML method had much higher noise than those transferred from the reference. The modified Langley method was used to calibrate the 940 nm channel with on-site measurement data. The V0 obtained with the modified Langley method compared to the Langley method was 1 % more accurate on stable and fine days. The general method was also used to calibrate the shortwave-infrared channels (1225, 1627, and 2200 nm) with on-site measurement data; the V0 obtained with the general method differed from that obtained with the Langley method of V0 by 0.8 %, 0.4 %, and 0.1 % in December 2015, respectively.

An unexpected and persistent increase in global emissions of ozone-depleting CFC-11.

The Montreal Protocol was designed to protect the stratospheric ozone layer by enabling reductions in the abundance of ozone-depleting substances such as chlorofluorocarbons (CFCs) in the atmosphere1-3. The reduction in the atmospheric concentration of trichlorofluoromethane (CFC-11) has made the second-largest contribution to the decline in the total atmospheric concentration of ozone-depleting chlorine since the 1990s 1 . However, CFC-11 still contributes one-quarter of all chlorine reaching the stratosphere, and a timely recovery of the stratospheric ozone layer depends on a sustained decline in CFC-11 concentrations 1 . Here we show that the rate of decline of atmospheric CFC-11 concentrations observed at remote measurement sites was constant from 2002 to 2012, and then slowed by about 50 per cent after 2012. The observed slowdown in the decline of CFC-11 concentration was concurrent with a 50 per cent increase in the mean concentration difference observed between the Northern and Southern Hemispheres, and also with the emergence of strong correlations at the Mauna Loa Observatory between concentrations of CFC-11 and other chemicals associated with anthropogenic emissions. A simple model analysis of our findings suggests an increase in CFC-11 emissions of 13 ± 5 gigagrams per year (25 ± 13 per cent) since 2012, despite reported production being close to zero 4 since 2006. Our three-dimensional model simulations confirm the increase in CFC-11 emissions, but indicate that this increase may have been as much as 50 per cent smaller as a result of changes in stratospheric processes or dynamics. The increase in emission of CFC-11 appears unrelated to past production; this suggests unreported new production, which is inconsistent with the Montreal Protocol agreement to phase out global CFC production by 2010.

Effect of Wind Speed on Moderate Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Depth over the North Pacific

The surface-wind speed influences on aerosol optical depth (AOD), derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua daily observations over the central North Pacific during the period 2003–2016, have been investigated in this study. The cloud coverage is relatively low over the present investigation area compared to other marine areas, which favors AOD derived from passive remote sensing from space. In this study, we have combined MODIS AOD with 2 m wind speed (U2m) on a satellite-pixel basis, which has been interpolated from National Centers for Environmental Prediction (NCEP) reanalysis. In addition, daily averaged AOD derived from Aerosol Robotic Network (AERONET) measurements in the free-troposphere at the Mauna Loa Observatory (3397 m above sea level), Hawaii, was subtracted from the MODIS column AOD values. The latter was to reduce the contribution of aerosols above the planetary boundary layer. This study shows relatively strong power-law relationships between MODIS mean AOD and surface-wind speed for marine background conditions in summer, fall and winter of the current period. However, previous established relationships between AOD and surface-wind speed deviate substantially. Even so, for similar marine conditions the present relationship agrees reasonable well with a power-law relationship derived for north-east Atlantic conditions. The present MODIS retrievals of AOD in the marine atmosphere agree reasonably well with ground-based remote sensing of AOD.

Ionospheric Trend Over Wuhan During 1947–2017: Comparison Between Simulation and Observation

AbstractSince Roble and Dickinson (1989), who drew the community's attention about the greenhouse gas effect on the ionosphere, huge efforts have been implemented on ionospheric climate study. However, direct comparison between observations and simulations is still rare. Recently, the Wuhan ionosonde observations were digitized and standardized through unified method back to 1947. In this study, the NCAR‐TIEGCM was driven by Mauna Loa Observatory observed CO2 level and International Geomagnetic Reference Field (IGRF) geomagnetic field to simulate their effects on ionospheric long‐term trend over Wuhan. Only March equinox was considered in both data analysis and simulation. Simulation results show that the CO2 and geomagnetic field have comparable effect on hmF2 trend, while geomagnetic field effect is stronger than CO2 on foF2 trend over Wuhan. Both factors result in obvious but different diurnal variations of foF2/hmF2 long‐term trends. The geomagnetic field effect is nonlinear versus years since the long‐term variation of geomagnetic field intensity and orientation is complex. Mean value of foF2 and hmF2 trend is (−0.0021 MHz/yr, −0.106 km/yr) and (−0.0022 MHz/yr, −0.0763 km/yr) for observation and simulation, respectively. Regarding the diurnal variation of the trend, the simulation accords well with that of observation except hmF2 results around 12 UT. Overall, good agreement between observation and simulation illustrates the good quality of Wuhan ionosonde long‐term data and the validity of ancient ionosphere reconstruction based on realistic indices driving simulation.