Sea Surface Temperature Front Research Articles

Retrievals of sea surface temperature fronts from SAR imagery

We present a new methodology to identify SST fronts of the Gulf Stream, using linear relationships between sea surface temperature (SST) gradients, and curl and divergence of wind stress fields, derived from high resolution (1 km) SAR data. The new approach uses a composite metric determined from the wind stress divergence and curl fields from individual SAR images. Multi‐stage spatial filtering, Wiener and Gaussian low‐pass filters, and a statistically‐based high pass spatial filter are applied to the derived wind stress curl and divergence fields. Results are significantly improved by restricting SAR imagery to cases where wind speed is less than 12 m/s, thus removing strong wind shear fronts. The method is demonstrated with SAR images of the Gulf Stream and has potential to be applied in near real time operations. The advantages of SAR imagery over optical sensors are its independence of cloud or night‐time conditions and high accuracy.

Atmospheric Dynamics Triggered by an Oceanic SST Front in a Moist Quasigeostrophic Model

Abstract To understand the atmospheric response to a midlatitude oceanic front, this paper uses a quasigeostrophic (QG) model with moist processes. A well-known, three-level QG model on the sphere has been modified to include such processes in an aquaplanet setting. Its response is analyzed in terms of the upper-level atmospheric jet for sea surface temperature (SST) fronts of different profiles and located at different latitudes. When the SST front is sufficiently strong, it tends to anchor the mean atmospheric jet, suggesting that the jet’s spatial location and pattern are mainly affected by the latitude of the SST front. Changes in the jet’s pattern are studied, focusing on surface sensible heat flux and on moisture effects through latent heat release. It is found that latent heat release due to moist processes is modified when the SST front is changed, and this is responsible for the meridional displacement of the jet. Moreover, both latent heat release and surface sensible heat flux contribute to the jet’s strengthening. These results highlight the role of SST fronts and moist processes in affecting the characteristics of the midlatitude jet stream and of its associated storm track, particularly their positions.

Covariability of Surface Wind and Stress Responses to Sea Surface Temperature Fronts

Abstract The responses of surface wind and wind stress to spatial variations of sea surface temperature (SST) are investigated using satellite observations of the surface wind from the Quick Scatterometer (QuikSCAT) and SST from the Advanced Microwave Scanning Radiometer on the Advanced Microwave Scanning Radiometer for Earth Observing System (EOS) (AMSR-E) Aqua satellite. This analysis considers the 7-yr period June 2002–May 2009 during which both instruments were operating. Attention is focused in the Kuroshio, North and South Atlantic, and Agulhas Return Current regions. Since scatterometer wind stresses are computed solely as a nonlinear function of the scatterometer-derived 10-m equivalent neutral wind speed (ENW), qualitatively similar responses of the stress and ENW to SST are expected. However, the responses are found to be more complicated on the oceanic mesoscale. First, the stress and ENW are both approximately linearly related to SST, despite a nonlinear relationship between them. Second, the stress response to SST is 2 to 5 times stronger during winter compared to summer, while the ENW response to SST exhibits relatively little seasonal variability. Finally, the stress response to SST can be strong in regions where the ENW response is weak and vice versa. A straightforward algebraic manipulation shows that the stress perturbations are directly proportional to the ENW perturbations multiplied by a nonlinear function of the ambient large-scale ENW. This proportionality explains why both the stress and ENW depend linearly on the mesoscale SST perturbations, while the dependence of the stress perturbations on the ambient large-scale ENW explains both the seasonal pulsing and the geographic variability of the stress response to SST compared with the less variable ENW response.

Variational assimilation of HF radar surface currents in a coastal ocean model off Oregon

The impact of assimilation of sea surface velocity fields observed by a set of high-frequency (HF) radars is studied using a three-dimensional ocean circulation model configured along the Oregon coast. The study period is June–July 2008 featuring upwelling and separation of the coastal currents into the adjacent interior ocean. The nonlinear model is based on the Regional Ocean Modeling System (ROMS) and the data assimilation (DA) component on the AVRORA system utilizing the representer-based variational algorithm. Assimilation proceeds in a series of 3-day windows, providing an analysis solution in each window and a 3-day forecast into the next window. Experiments with two different initial condition error covariances are compared (one is dynamically balanced, based on the linearized equation of state, temperature-salinity relation, and geostrophic and thermal wind balance relations and the other is multivariate unbalanced). While the assimilation impact is statistically better in the case of the balanced covariance, the case with the unbalanced covariance also provides sensible improvement in terms of surface velocity and sea surface temperature (SST) model-data forecast statistics. The analysis of representer functions shows that even if the initial condition error covariance is unbalanced, the correction fields at the model initial time are partially balanced after each dynamical field is smoothed independently, due to inherent dynamical properties of the adjoint model. Assimilation of the HF radar surface currents improves not only surface velocity forecasts, but also geometry of the upwelling SST front and the sea surface height (SSH) slope near the coast, as verified against unassimilated satellite SSH and SST data. The assimilation also alters the latitudinal distribution of the time-averaged offshore transport. Combined HF radar velocity and other observations, e.g., altimetry, is needed to better constrain surface geostrophic currents in the entire model domain, including the area not covered by the HF radar data.

Atmospheric Circulations Induced by a Midlatitude SST Front: A GCM Study

Abstract The atmospheric effects of sea surface temperature (SST) anomalies over and near western boundary currents are a matter of renewed interest. The general circulation model (GCM) of the Laboratoire de Météorologie Dynamique (LMD-Z) has a zooming capability that allows a regionally increased resolution. This GCM is used to analyze the impact of a sharp SST front in the North Atlantic Ocean: two simulations are compared, one with climatological SSTs and the other with an enhanced Gulf Stream front. The results corroborate the theory developed previously by the present team to explain the impact of oceanic fronts. In this theory, the vertical velocity at the top of the atmospheric boundary layer has two components: mechanical and thermal. It is the latter that is dominant in the tropics, while in midlatitudes both play a role in determining the wind convergence above the boundary layer. The strengthened SST front does generate the previously predicted stronger ascent above the warmer water south of the front and stronger descent above the colder waters to the north. In the GCM simulations, the ascent over the warm anomalies is deeper and more intense than the descent.

Fisheries applications of remote sensing: An overview

During the past 40 years the fisheries productivity of the world has been declining due to pressures from overfishing, habitat change, pollution, and climate change. Sustainable use of marine resources requires effective monitoring and management of the world's fish stocks. Remote sensing techniques are being used to help manage fisheries at sustainable levels, while also guiding fishing fleets to locate fish schools more efficiently. Fish tend to aggregate in ocean areas that exhibit conditions favored by specific fish species. Some of the relevant oceanographic conditions, such as sea surface temperature, ocean color (productivity) and oceanic fronts, which strongly influence natural fluctuations of fish stocks, can be observed and measured by remote sensors on satellites and aircraft. The remotely sensed data are provided in near-real time to help fishermen save fuel and ship time during their search for fish; to modelers who produce fisheries forecasts; and to scientists who help develop strategies for sustainable fisheries management. This article describes how acoustic, optical and radar sensors on ships, satellites and aircraft are used with forecast models to improve the management and harvesting of fisheries resources.

Dependence of the climatological axial latitudes of the tropospheric westerlies and storm tracks on the latitude of an extratropical oceanic front

Major “storm tracks”, where migratory cyclones and anticyclones recurrently develop, are observed around midlatitude oceanic frontal zones with strong meridional gradient of sea‐surface temperature (SST). A set of atmospheric general circulation model experiments is performed with zonally uniform SST prescribed at the model lower boundary. The latitudinal SST profile for each hemisphere is characterized by a single front. The frontal latitude is varied systematically from one experiment to another, while the intensity of the frontal gradient is kept unchanged. Though idealized, the experiments reveal a climatological tendency for a low‐level storm track to be organized along or slightly poleward of the SST front if located in the subtropics or midlatitudes. As a surface manifestation of an eddy‐driven polar‐front jet (PFJ), surface westerly axis tends to form on the poleward flank of the front. This anchoring effect of the SST front is also hinted at upper levels, but the climatological positions of the storm track and PFJ are less sensitive to the frontal latitude. For the SST front at subpolar latitude, the joint primary axes of the upper‐level storm track and PFJ form in midlatitudes away from the SST front. Their positions correspond to their counterpart simulated with a particular SST profile from which frontal gradient has been removed, suggesting that the anchoring effect of a subpolar SST front on the storm track and PFJ is overshadowed by atmospheric internal dynamics, namely, the self‐maintenance mechanism of a midlatitude storm track and PFJ through their interactions.

Spatial and temporal statistics of sea surface temperature and chlorophyll fronts in the California Current

The statistics of sea-surface fronts detected with the automated histogram method were studied in the California Current using sea-surface temperature (SST) and chlorophyll-a concentration (Chl) images from various satellite sensors. Daily maps of fronts were averaged into monthly composites of front frequency (FF) spanning 29 years (1981–2009) for SST and 14 years (1997–2010) for Chl. The large-scale distributions of frontal frequency of both SST (FFsst) and of Chl (FFchl) had a 500–700 km wide band of elevated values (4–7%) along the coast that roughly coincided with the area of increased mesoscale eddy activity. FFsst and FFchl were positively correlated at monthly and seasonal frequencies, but the year-to-year variations were not significantly correlated. The long-period (1 year and longer) variability in FFsst is influenced by the large-scale SST gradient, while at shorter timescales the influence of the Coastal Upwelling Index is evident. In contrast with FFsst, FFchl variability is less related to the coherent large-scale forcing and has stronger sensitivity to local forcings in individual areas. Decadal-scale increasing trends in the frequency of both SST and Chl fronts were detected in the Ensenada Front area (general area of the A-Front study) and corresponded to, respectively, trends towards colder SST and increasing chlorophyll-a concentration.

Sea surface height oscillation with quasi-four-month period along the continental slope in the northern South China Sea

The sea surface height oscillation with a quasi-four-month period (SSHO4) along continental slope in the northern South China Sea (NSCS) is detected using satellite altimeter data and an ocean model simulation. The SSHO4 is at southwest of Dongsha Island, and is characterized by a wavelength of ∼600 km and a southwestward phase speed of ∼0.1 m/s. Crossing the climatological background SST front, geostrophic currents corresponding to the SSHO4 generally induce sea surface temperature (SST) “tongues” during January–March. The cold and warm SST tongues appear southwest of cyclonic and anticyclonic eddies, respectively. The distance between the warm and cold SST tongues is about half the wavelength of the SSHO4. The geostrophic currents play an important role in lateral mixing, as manifested by the SST tongue phenomena in the NSCS.

Toward Automated Identification of Sea Surface Temperature Front Signatures in Radarsat-2 Images

Abstract The Canadian Forces Meteorology and Oceanography Center produces a near-daily ocean feature analysis, based on sea surface temperature (SST) images collected by spaceborne radiometers, to keep the fleet informed of the location of tactically important ocean features. Ubiquitous cloud cover hampers these data. In this paper, a methodology for the identification of SST front signatures in cloud-independent synthetic aperture radar (SAR) images is described. Accurate identification of ocean features in SAR images, although attainable to an experienced analyst, is a difficult process to automate. As a first attempt, the authors aimed to discriminate between signatures of SST fronts and those caused by all other processes. Candidate SST front signatures were identified in Radarsat-2 images using a Canny edge detector. A feature vector of textural and contextual measures was constructed for each candidate edge, and edges were validated by comparison with coincident SST images. Each candidate was classified as being an SST front signature or the signature of another process using logistic regression. The resulting probability that a candidate was correctly classified as an SST front signature was between 0.50 and 0.70. The authors concluded that improvement in classification accuracy requires a set of measures that can differentiate between signatures of SST fronts and those of certain atmospheric phenomena and that a search for such measures should include a wider range of computational methods than was considered. As such, this work represents a step toward the goal of a general ocean feature classification algorithm.

Eddy effects on sea surface temperature and sea surface wind in the continental slope region of the northern South China Sea

Warm and cold sea surface temperature (SST) tongues on weather timescales are detected in the continental slope region of the northern South China Sea (NSCS), and their effects on sea surface wind are studied, using satellite observations. Crossing the basin‐scale SST front, geostrophic currents between cyclonic and anticyclonic eddies induce the warm and cold SST tongues during the northeast monsoon. Corresponding to the warm and cold SST tongues, the sea surface wind is highly uneven in spatial distribution. Its speed is faster (slower) over the warm (cold) SST tongues than the surrounding areas. The SST and sea surface wind non‐uniformity, in space, shifts southwestward with eddy motion, along the continental slope. These new findings from satellite observations give us an opportunity to study oceanic eddy's roles in ocean‐atmosphere interaction on weather timescales.

南大洋における海洋フロントの南北シフト

The Southern Ocean plays an important role in the global climate system both at present and in the geologic past. To resolve the causes and processes of atmospheric CO2 change, it is important to understand the mechanisms and processes of sub-systems in the Antarctic Cryosphere such as change of biological productivity, sea-surface temperature, surface water frontal system, sea ice distribution, and the Antarctic Ice Sheet during the glacial-interglacial climate cycle. A large number of float observations made recently suggest that mid-depth Southern Ocean temperatures rose 0.17°C between the 1950s and 1980s. The Southern Ocean is warming faster than the global oceans, and this is concentrated within the Antarctic Circumpolar Current (ACC). Warming is consistent with a poleward shift of the ACC, probably driven by long-term poleward shifts in the winds of the region, as represented by the southern annular mode. Changes to the extent of Antarctic sea ice are difficult to quantify for the pre-satellite observation era. However, a substantially larger set of proxy records based on whaling positions indicates that a larger southward shift of the summer sea ice edge occurred between the mid-1950s and early 1970s. In the glacial to interglacial cycle, ice-rafted debris (IRD) is an important proxy for reconstructing past iceberg discharges and sea ice expansions. However, it is necessary to specify the origin of IRD in the Southern Ocean, because IRD deposition on the pelagic seafloor is controlled not only by the dynamics of the Antarctic ice sheet but also by surface water conditions such as sea-surface temperature and oceanic front migrations. For example, several layers rich in volcanic tephra were deposited in the eastern Atlantic sector of the Southern Ocean. Deposition of the tephra-rich IRD layers was controlled by changes in sea-surface temperature and sea ice conditions in the Polar Frontal Zone of the South Atlantic, rather than Antarctic ice sheet dynamics. Thus, IRD deposition is a signal of the expansion of sea ice in the South Atlantic. According to IRD records, it seems that sea ice expansion events occurred suddenly in the Atlantic sector of the Southern Ocean during the last glacial period.

Temporal Scale of Sea Surface Temperature Fronts Revealed by Microwave Observations

Sea surface temperature (SST) data for three years from the Advanced Microwave Scanning Radiometer for the Earth Observing System are used to statistically evaluate the temporal scales of the global SST fronts (SSTFs). Using the entropy-based edge detection method which is very resistant to impulsive noises, temporal autocorrelation of the dissimilarities of two SST groups across the SSTF is calculated in 10-km-gridded map. In general, the derived temporal scales, defined as e-folding scales in this study, range from 10 to 40 days. Long temporal scales of up to 100 days are found in areas where the stationary ocean currents maintain the frontal structures.

Spatial and temporal changes in sea surface temperature, circulation and subpolar front of the East Sea (Japan Sea) during the last 130,000 years

In order to reconstruct spatial and temporal changes in sea surface temperature (SST) of the East Sea (Japan Sea) on glacial–interglacial time scale, alkenone temperature records from the both Korean and Japan margins have been investigated for the period over the last 130 kyr. Results show that the temperature gradient between the Korean and Japan margins was relatively small (~ 2 °C) during the warm interval of the interglacial period (MIS 5e). But it was large (~ 10 °C) during the transitional period from the interglacial to the glacial (MIS 5a and b). The temperature of the Korean margin was colder than that of the Japan margin during the transitional period. Based on the reconstructed alkenone temperature, temporal changes in surface circulation and subpolar front (SPF) have been investigated. During the interglacial period when sea level was higher than today (MIS 5e), the influx of the Tsushima Warm Current (TWC) was enhanced and the both Korean and Japan margins were influenced by the warm water. At that time, the SPF appears to be located in the northern part compared to today. During the transitional period when the sea level was lower than today (MIS 5a and b), the TWC volume transport was reduced contributing to the lower SST. Its effect on the surface temperature appears to be larger along the Korean margin than the Japan margin, indicating that the strength of the East Korea Warm Current appears to be strongly correlated with the TWC volume transport. The SPF would displace southward orienting from southwest to northeast at that time. During the glacial period when the sea level was very lower (~ 100 m deep), the influx of warm water was almost completely restricted and the cold water expanded into the southern area. The SPF would disappear at that time. Model simulation results also support the relationship between the TWC volume transport and surface circulation and the SST.

Relationship between albacore ( Thunnus alalunga) fishing grounds in the Indian Ocean and the thermal environment revealed by cloud-free microwave sea surface temperature

Using cloud-free Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) sea surface temperature (SST) and daily set longline fishery data, we studied the relationship between albacore (ALB) fishing grounds and thermal conditions in the southern Indian Ocean. SST and Jensen–Shannon divergence (JSD) maps with a daily spatiotemporal resolution were related to sites with high catches per unit effort (CPUE) (>11 fish/10 3 hooks). A high JSD is considered to be an index of a SST front. In winter, high CPUE occurred in the vicinity of the North Subtropical Front ( Belkin and Gordon, 1996), where SST was 15–19 °C and JSD was 0.3–0.9. Histograms of the high CPUE plotted against SST and JSD indicated that 95% of the high CPUEs were in the 16–18.5 °C SST range and 97% were in the 0.4–0.9 JSD range. These ranges of SST and JSD are optimum ranges. These cloud-free SST/JSD analyses clearly demonstrate the seasonal north–south movement of the optimum SST and JSD band, which corresponds to the North Subtropical Front in the southern Indian Ocean. Monthly maps of joint probability density (JPD) with the optimum ranges of SST and JSD revealed that high CPUEs are located in the narrow bands with high JPD (>50%).

Deep Atmospheric Response to the Spring Kuroshio over the East China Sea*

AbstractThe atmospheric response to the spring Kuroshio Front over the East China Sea is investigated using a suite of high-resolution satellite data and a regional atmospheric model. The atmospheric response appears to extend beyond the marine atmospheric boundary layer, with frequent occurrence of cumulus convection.In spring, Quick Scatterometer (QuikSCAT) wind speed shows a clear effect of sea surface temperature (SST), with high (low) wind speed observed over the warm (cold) tongue. This in-phase relationship between SST and surface wind speed is indicative of SST influence on the atmosphere. Wind convergence is found on the warmer flank of the Kuroshio Front, accompanied by a narrow rainband. The analysis of satellite-borne radar measurements indicates that deep convection appears over the Kuroshio warm tongue in the spring season, with enhanced convective precipitation, frequent occurrence of cumulus convection, and increased precipitation (cloud) tops in altitude. These deep convective activities along the Kuroshio warm tongue are further supported by enhanced lightning flash rate observed by satellite and atmospheric heating estimated by a Japanese reanalysis.The Weather Research and Forecasting (WRF) model is used to investigate the precipitation response to the spring Kuroshio SST front over the East China Sea. Forced by observed SST [control (CTL)], the model well simulates a narrow band of precipitation, high wind speed, and surface wind convergence that closely follows the Kuroshio warm current, consistent with satellite observations. This narrow rainband completely disappears in the model when the SST front is removed by horizontally smoothed SST (SmSST). The results show that it is convective precipitation that is sensitive to the Kuroshio SST front. A case study for an eastward-moving extratropical cyclone indicates that convective precipitation increases its intensity and duration in the CTL run compared to the SmSST run. Local enhancement of upward sensible and latent heat fluxes and convective instability in the lower atmosphere are the key to anchoring the narrow band of convective precipitation that closely follows the Kuroshio.

Ocean Preconditioning of Cyclone Nargis in the Bay of Bengal: Interaction between Rossby Waves, Surface Fresh Waters, and Sea Surface Temperatures*

Abstract An in-depth data analysis was conducted to understand the occurrence of a strong sea surface temperature (SST) front in the central Bay of Bengal before the formation of Cyclone Nargis in April 2008. Nargis changed its course after encountering the front and tracked along the front until making landfall. One unique feature of this SST front was its coupling with high sea surface height anomalies (SSHAs), which is unusual for a basin where SST is normally uncorrelated with SSHA. The high SSHAs were associated with downwelling Rossby waves, and the interaction between downwelling and surface fresh waters was a key mechanism to account for the observed SST–SSHA coupling. The near-surface salinity field in the bay is characterized by strong stratification and a pronounced horizontal gradient, with low salinity in the northeast. During the passage of downwelling Rossby waves, freshening of the surface layer was observed when surface velocities were southwestward. Horizontal convergence of freshwater associated with downwelling Rossby waves increased the buoyancy of the upper layer and caused the mixed layer to shoal to within a few meters of the surface. Surface heating trapped in the thin mixed layer caused the fresh layer to warm, whereas the increase in buoyancy from low-salinity waters enhanced the high SSHA associated with Rossby waves. Thus, high SST coincided with high SSHA. The dominant role of salinity in controlling high SSHA suggests that caution should be exercised when computing hurricane heat potential in the bay from SSHA. This situation is different from most tropical oceans, where temperature has the dominant effect on SSHA.

ASAR imaging for coastal upwelling in the Baltic Sea

Analysis of Envisat Advanced Synthetic Aperture Radar (ASAR) and Aqua/Terra Moderate Imaging Spectrometer (MODIS) infrared (IR) imagery of coastal upwelling in the southeastern Baltic Sea is presented. It is found that upwelling features are well distinct in the SAR images, and the leading imaging mechanism appears to be the change of the marine atmospheric boundary layer (MABL) stratification over the sea surface temperature (SST) front. This finding is supported by model calculations of the MABL transformation supplemented with the SAR backscatter calculations based on the CMOD4 model. In addition an empirical dependence of the SAR contrasts over the upwelling region on the wind speed and the SST drop is suggested. Finally, surface slicks accumulated in the sea surface current convergence zones generate additional distinct features in SAR imagery. This effect is interpreted within the framework of the coastal current circulation model based on analysis of the SST snapshot.

Sea Level Pressure Minimum along the Kuroshio and Its Extension*

Abstract Atmospheric effects of sea surface temperature (SST) fronts along the Kuroshio and Kuroshio Extension (K-KE) are investigated by examining spatial characteristics of the climatological sea level pressure (SLP), surface winds and surface heat flux (Q) fields based on an in situ observation dataset. A hydrostatic effect of the SST front is observed during the northwesterly monsoon characterized by a westward-extending low-SLP wedge (trough) slightly south of the peak in Q along the K-KE. Ageostrophic surface westerlies crossing SLP isobars toward a trough center are found north of the low-SLP wedge apparently because of the eastward acceleration by the vertical mixing effect. This feature of the ageostrophic winds is less pronounced south of it, a north–south asymmetry arising as vertical mixing accelerates (decelerates) eastward ageostrophic winds north (south) of it. While the SLP trough near the SST front is found nearly year-round except for summer, its meridional location seasonally migrates probably due to the change in the mean surface flow. Regional atmospheric model experiments are conducted to examine the effect of the SST front on the overlying atmosphere. The observed features in winter are adequately simulated when high-resolution SST is prescribed as the boundary condition. The strong Q along the K-KE and resultant SLP trough and ageostrophic surface winds are absent when the SST boundary condition is smoothed in space to weaken the SST front. These results illustrate that the cross-frontal change in Q is of great importance to leave the SST imprint on the overlying atmosphere via hydrostatic and vertical mixing adjustments.

Epipelagic fish distributions in relation to thermal fronts in a coastal upwelling system using high-resolution remote-sensing techniques

Abstract Reese, D. C., O'Malley, R. T., Brodeur, R. D., and Churnside, J. H. 2011. Epipelagic fish distributions in relation to thermal fronts in a coastal upwelling system using high-resolution remote-sensing techniques. – ICES Journal of Marine Science, 68: 1865–1874. Coastal upwelling systems are characterized by substantial spatial and temporal variability with respect to surface conditions, with fauna patchily distributed and high abundances in localized areas. Examining habitat associations on finer spatial scales than previous studies have been able to achieve would advance the understanding of important marine coastal ecosystems. This study evaluates the spatial and temporal relationships of single fish and fish schools with sea surface temperature (SST) fronts in the northern California Current upwelling system, using lidar (light detection and ranging) from an aircraft to sample surface waters over the continental shelf. High-resolution data were collected on the distribution of surface nekton and SST, then the locations of fish were analysed with respect to their proximity to SST fronts using GIS spatial analyses. Both fish schools and solitary fish were located significantly closer to fronts than would be expected by chance. The association of fish to fronts varied with the progression of the upwelling season such that fish associated less with fronts under stronger upwelling conditions. The relationships observed indicate the importance of thermal features to fish as a habitat component in a variable upwelling environment and have implications for management and conservation.