This application presents essential weather data from the past 24 hours. By default, it displays plots featuring 24-hour measurements from Site 200 (LLNL), along with the latest readings from selected instruments at both Site 200 and Site 300.
Lawrence Livermore National Laboratory (LLNL) collects on-site meteorological data to meet federal, state, and local regulatory requirements and to ensure the safety of both the environment and the public. Accurate, real-time meteorological monitoring is essential for assessing the transport and dispersion of airborne materials, evaluating the impacts of planned and accidental releases, and performing required dose calculations for regulatory compliance. On-site data is preferred over off-site sources, as it more accurately represents local conditions and is readily available during emergencies. Beyond regulatory compliance, LLNL’s meteorological data supports facility design, site planning, emergency management, and numerous operational activities, including fire fighting, environmental restoration, energy management, and regional climate studies. This data serves as a vital resource for both internal projects and external collaborations, helping to protect public health and guide responsible facility operations.
The climate of the Livermore Valley can be characterized as having mild, rainy winters and warm, dry summers. The mean annual temperature is about 15°C. Temperatures range from -5°C during some pre-dawn mornings in the winter, to 40°C in a few summer afternoons.
It can be seen from this data that the prevailing wind direction is from the southwest. This is the predominant wind direction during the summer. The wind does blow from the northeast and this is primarily during the winter.
Most of the precipitation occurs between October an April with very little rainfall during the summer months. The highest and lowest annual rainfalls on record for the city of Livermore are 812 and 122 mm (31.95 and 4.82 inches). The average annual rainfall is 368 mm (14.48 inches) based on 127 years of data.
Livermore’s climate data support a wide range of scientific and operational activities at LLNL.
Meteorological data collected at LLNL are used to demonstrate compliance with federal, state, and local laws, regulations, and orders. DOE directives require LLNL to collect sufficient meteorological data to assess the impact of hazardous material releases on the environment and the public. On-site meteorological monitoring is required to accurately assess the transport and diffusion of airborne materials and the impacts of planned and unplanned airborne releases on public health. In addition, DOE sites are required to have on-site programs that can provide data used to perform the required dose calculations specified in 40 CFR Part 61, Subpart H, National Emission Standards for Hazardous Air Pollutants; Standards for Radionuclides, which states:
Compliance with this standard shall be determined by calculating the highest effective dose equivalent to any member of the public at any offsite point where there is a residence, school, business, or office.
DOE Order 458.1 Radiation Protection of the Public and the Environment and DOE-HDBK-1216-2015 Environmental Radiological Effluent Monitoring and Environmental Surveillance require each DOE site to have a meteorological program that is appropriate to the site’s activities, topography, and distance to critical receptors. DOE requires that meteorological measurements must be representative of the conditions that determine transport and dispersion at the site. Furthermore, real-time meteorological data should be available to assess adequately, in accord with DOE Order 151.1C, the actual or potential on-site and off-site consequences of an emergency. Meteorological information can also be used to assess potential consequences of radiological releases from projected new or modified facilities, as well as consequences of actual accidental radiological releases. Livermore Site and Site 300 are both NARAC (National Atmospheric Release Advisory Center) sites as designated by DOE. NARAC was developed at LLNL to provide real-time assessments of the impact of radiological releases to the atmosphere anywhere in the world.
Both the Livermore Site and Site 300 are designated as NARAC (National Atmospheric Release Advisory Center) sites by DOE. NARAC, developed at LLNL, provides real-time assessments of the impact of radiological releases to the atmosphere anywhere in the world, supporting emergency response and regulatory compliance.
All uses of the LLNL meteorological database must follow established EPA guidance, including:
LLNL also maintains a quality assurance program that meets the performance requirements described by EPA and DOE. Volume IV of EPA’s Quality Assurance Handbook for Air Pollution Measurement Systems, Version 2 (U.S. EPA 2008), commonly called Volume 4, provides guidance for making judgments about the validity of meteorological data and accuracy of meteorological measurement systems.
Atmospheric dispersion calculations range in complexity from very simple analytical expressions, requiring little or no meteorological data, to complex super-computer models that can accept extensive data sets. The EPA Guideline on Air Quality Models (U.S. EPA Revised 2005) describes its preferred computer models. Another good source is the Handbook on Atmospheric Diffusion (Hanna, Briggs, and Hosker 1982). The dispersion model should be appropriate for the site and application. The assumptions upon which a dispersion model is based should be reasonable, completely documented, and scientifically defensible. The dispersion model should be realistic and yet yield conservative predictions. The data used in these models should be based on data from the appropriate time period. For example, if a proposed experiment has the potential for a release during the daytime, then the probability tables and wind roses that are to be used with the model should include meteorological data taken exclusively during the daytime.
The U.S. EPA requires the use of mandated computer models to demonstrate compliance with 40 CFR Part 61, Subpart H. LLNL’s primary calculation tool for the estimation of dose and risk is the computer model CAP88-PC, developed by U.S. EPA’s Office of Radiation Programs (Parks 1992). The meteorological input to CAP88-PC consists of a joint-frequency distribution of wind direction and atmospheric stability, average wind speed for each combination of wind direction and stability, average mixing-layer depth, annual average temperature, and annual rainfall.
Off-site meteorological data, such as the data collected at National Weather Services (NWS) stations, may be used if the meteorological conditions at the station are similar to on-site conditions. The nearest NWS stations are at the Livermore Airport, the Hayward Air Terminal, Oakland Airport, and Stockton; but meteorological conditions at these locations may not accurately represent dispersion conditions at the Livermore site or Site 300. Moreover, it may be difficult to retrieve data from off-site meteorological stations in a timely manner during emergencies. For these reasons, among others, on-site meteorological monitoring systems are employed.
DOE Order 420.1B sets the requirements for evaluating facility safety, including the assessment of hazards posed by natural phenomena such as flood, wind and lightning. Temperature and humidity data can be used to plan efficient air conditioning and space heating of proposed facilities. Hood exhaust re-entrainment and building-wake effects can be modeled using wind-flow data provided by on-site monitoring. Facility designers should use meteorological data when proposing stacks and cooling towers. U.S. EPA guidance for stack design can be found in the Guideline for Determination of Good Engineering Practice Stack Height (U.S. EPA 1985 EPA Publication No. EPA–450/4–80–023R).
LLNL’s meteorological data supports a wide range of projects and operations, including:
Environment, Safety, and Health (ES&H)is responsible for monitoring the effects of operations conducted at the LLNL Livermore site and Site 300 on the environment and the public. Meteorological monitoring represents one aspect of ES&H's monitoring responsibilities. ES&H has responsibility for the maintenance and calibration of the Livermore site and Site 300 towers. ES&H is responsible for the removal, calibration, refurbishment, and certification of the sensors. Sensor maintenance/replacement/calibration is performed as necessary based on the results of weekly inspections. Wind speed, wind direction, temperature and relative humidity sensors are calibrated and replaced annually as required by DOE-HDBK-1216-2015. Maintenance and calibration is performed by qualified and trained personnel in ES&H.
Every year the meteorological systems are audited by an independent auditor in accordance with EPA guidance set forth in Volume 4. Audits are a critical component of the Quality Assurance (QA) plan. Additionally, an internal calibration is conducted by LLNL personnel.
